» Advanced

Go Back   Shooters Forum > Gunsmithing Forums > Gunsmithing
Register FAQ Members List Donate Calendar Search Today's Posts Mark Forums Read



Reply
 
LinkBack Thread Tools Rating: Thread Rating: 2 votes, 5.00 average. Display Modes
  #1  
Old 05-30-2008, 08:36 PM
Beartooth Regular
 
Join Date: May 2008
Posts: 100
Question Piller bedding vs Glass bedding


Registered Users do not see the above ad.


I have a Cooper Classic Mod 22 in 22-250 AI . Had a after market Mike Rock 5R 8" twist barrel installed.( Didn't like the 14" factory BBL) They blew it on the Dura coat painting. So I sent it back plus I complained that the rifle averaged about 3/4" groups . I wanted them to shoot it. They didn't but they did say that there was some wood to metal contact and they recommended a piller bedding Job. Others have said glass bedding is actually better for a sporter/hunter rifle.When I shot 75gr A-Maxs they weren't doing any better then 1"MOA . This is my predator rifle.Stock doesn't ride the bags very well. So what is best type of bedding?
Reply With Quote
  #2  
Old 05-30-2008, 08:50 PM
Moderator
 
Join Date: Dec 2002
Location: Jefferson Parish (via N.O.)
Posts: 9,035
IF there is any difference in a well done glass bed job and a pillar bed job, I can't detect it...but pillar bedding is proably easier to get right, so I'd go for that.

Realize that the combination of you, the rifle, and the stock that doesn't ride the bags very well might not be able to do any better than 3/4". Stock that doesn't right right (or whatever terms you want to use for how a stock is supose to react to a bag) bothers me more than the bedding. That stock is moving a bit on the bag BEFORE the bullet clears the barrel (not much...but recoil doesn't start at bullet exit...it starts at bullet movement), getting it to ride the bag consistently would be on the "to do" list (and I might change bag type/shape rather than whittle on the stock).

Last edited by ribbonstone; 05-30-2008 at 08:53 PM.
Reply With Quote
  #3  
Old 05-30-2008, 10:47 PM
faucettb's Avatar
Beartooth Regular
 
Join Date: Feb 2004
Location: Peck, Idaho
Posts: 12,620
Welcome to the forum Ironworker. Rules are simple, be nice and join in.

Actually piller bedding is usually done as an adjunct to glassbedding. Combining the two usually results in the ideal bedding job. I've been using Brownell's Acra-glass for lots of years and Brownell's also sells both the piller bedding kits and individual pillers.

Here's an article on bedding that may give you some insight into bedding and what it does for a rifle.

Understanding Barrel Bedding

ribbonstone is right, you may not be able to obtain better accuracy than 3/4 inch groups. Playing with different bullets, powders and seating depth are some of the keys to better accruacy. I've been glassbedding and piller bedding rifles for better than 30 years and on the average I've found a 10 percent increase in accuracy, but often more.

Keep in mind that you may not get much barrel life from a 1 in 8 twist 22-250 at high velocities. They work at 223 velocities, but fast twist barrels and velocities above 3500 fps tend to lead to much shorter barrel life in a .224 bore.
__________________
Bob from Idaho
Reply With Quote
  #4  
Old 05-31-2008, 08:12 AM
markkw's Avatar
Beartooth Regular
 
Join Date: Dec 2004
Location: FL
Posts: 1,946
Bob,

From the article:
Quote:
Before going further, however, let me again emphasize that slender, lightweight barrels--say, less than .575 inch at the muzzle--do tend to group best when the stock is exerting dampening pressure, but it might be at the expense of a wandering zero and a rifle that's temperamental


The major problem with that statement is that high points in stock or pillars of hard bedding compound placed near the end of the stock do NOT provide a "dampening effect" they provide nothing more than a "pivot point" and turn a simple cantilever problem into a complex dual-loading problem. With a pure cantilever arrangement, you are dealing with an extension that is securely fixed at one end (barrel to the receiver) - in the dual-loading arrangement you have a non-fixed support at some point between the anchor base (receiver) and the free end (muzzle) which now allows for vertical and horizontal movement in two different directions at the same time, between the anchor and pillar and between the pillar and free end. Since the barrel in this case is not fixed or anchored to the pillar, it is free to lift off the pillar and also bend just as a stick does when you try breaking it over your knee. As the barrel flexes, the surface contact area between pillar and barrel exterior is reduced to very small points at the front and rear of the pillar when the muzzle goes down and to a single point in the center of the pillar when the muzzle goes up. All during the movement cycle, the barrel is subjected to additional injection of vibration energy caused by the hard surface of the steel contacting the hard surface of the stock/bedding compound. The key to improving accuracy is by reducing the amount of vibration and flex in the barrel. If you're setting-up a condition where additional secondary vibration is being induced into the barrel, you are compounding the problem rather than reducing it. To understand this, drop a coin onto your kitchen counter and see what happens when the two solid objects impact, then drop the same coin onto the same counter but this time cover the counter with a folded dish towel and see what happens. As you already know, the coin will not bounce and rattle around taking X amount of time to come to rest - the same applies to a gun barrel.

I've been on the mechanical approach for more than seven years and it's brought many things to light that were previously overlooked because focusing on ballistics takes your attention away from the mechanical issues which are what you need to be concerned with because if the mechanical issues are not addressed, anything you do with the ballistics becomes almost a moot point. Ignoring the mechanical issues on a gun is like building a bridge then limiting the traffic flow to conform with the design standards of the bridge rather than building the bridge to conform to the traffic loading and atmospheric/geographical/environmental conditions. The same holds true for a rifle when you build it and then accept whatever loading conditions the rifle will allow and often times acceptable window of operation is extremely small or shows itself at a point where you don't want to be.

If you look at a barreled action as a single leg cantilever tuning fork, the sear releasing allowing movement of the firing pin causes vibrations to be induced into the bolt, while these vibrations don't have much amplitude, they run the length of the receiver and continue through the solid joint and into the barrel where they cause the entire assembly to vibrate out to the muzzle. The next action is the firing pin impacting the primer which produces a second set of vibration pulses to be induced into the gun. When the primer ignites, now you have additional vibration pulses being induced by the pressure change. Same when the powder ignites, when the bullet breaks free of the hold the case neck has on it, enters the rifled and so on until it's clear of the muzzle there are numerous points at which vibration is induced into the assembly. Furthermore, you also have annular pressure waves working on the barrel in addition to the vibration energy. As each vibration is induced into the assembly, the pulses travel between the receiver and the muzzle as dictated by their frequency. As each set of vibrations are induced, the add and subtract from one another as they pass each other. Just as if you toss a small stone in a pond and create small ripples, you can throw a large stone in same spot immediately after the small one and see the small ripples riding on top of the larger ones - the same applies to vibrations in metal.

Even if you were to obtain the utmost in loading consistency producing a standard deviation of just 1fps, the muzzle can be in any one of hundreds or thousands of positions within it's cumulative deviation range when the bullet actually clears the muzzle. Obtaining perfect timing of having the bullet clear the muzzle when the muzzle is in a specific position is impossible. This is why one must view the mechanical issues with as much vigor as the load building issues. This is why you will likely notice that following the application of hard bedding compound will considerable change the POI and load parameters - reason being is that you are changing the vertical direction, amplitude and frequency of the vibrations and annular wave actions. As the quote above also clearly notes, applying a single hard pressure point near the end of the stock will usually end with "wandering zero" which is directly related to the change in the mechanical conditions that compound the both the mechanical and ballistic conditions more than they need be since all is left to nothing but chance beyond a certain point in the load tuning process.

Annular energy waves are about completely ignored yet they are oh so important when considering the mechanical portion of the issue. Annular waves cause deliberate movement of the barrel and when that movement is interrupted in one direction by solid bedding/stock contact but not in the other direction, all of the mechanical parameters change often resulting in major POI changes that are directly proportional to the load parameters. For example, if you raise your car on a jack and let all the air out of the tire, you don't see any change in the position of the car no matter if the tire is inflated or not. If you leave the tire firmly in contact with the ground, movement of the car vertically will be directly proportional to both the speed at which the pressure change in the tire occurs and by the amplitude of the pressure change. The barrel sitting in solid bedding will react in the same manner since you have deliberately removed its ability to move equally in all directions.

Taking all this into account, you are left with the problem of how to control the movement of the barrel without introducing additional mechanical issues into the myriad of cause and effect relationships controlling the resultant function of the system as a whole. Thus, one must view the problem as a whole yet break it down into sub-components so as to connect the relationship of change in one component to the resultant change in all the other components. With this in mind, let's look at metal to metal pillar bedding - no matter what the combination of joints you make between the receiver and stock, you are not changing the basic fact that no matter what substance you put between the stock and receiver, the sole supporting unit of the assembly is still the stock. Combine that fact with the known theories of vibration transmission in steel alloys and you'll quickly understand that the better you anchor the receiver, the better it performs as a reflection point for the vibrations/energy pulses. Take the wood handle off your 10# sledge hammer and replace it with a piece of solid steel barstock, you'll immediately note the amount of vibration and impact energy transferred to your hands upon striking a solid object like a large rock with the head of the hammer is considerably increased. The same holds true for the receiver on a gun since the receiver is the anchor point for the barrel just as the hammer head is the anchor point for the handle. Another consideration is that many have gone to using aluminum blocks between the stock and receiver - to this I ask you to consider the fact that if you cannot obtain proper contact points between the receiver and stock, how does this differ when you try to make the contact point between the metal pillar or block and stock? - - Is this not of the same following, removing one problem and replacing it with now several additional problems serves what purpose? Now, not only must you contend with the original issue of creating a receiver to stock connection, now you must also create a block/pillar connection to the stock, a connection between the receiver and block/pillar as well. Then you have the issue of contending with the additional problems associated when connecting dissimilar metals such as aluminum and steel where you are creating a joint that is now electrically active in that electrolysis corrosion will begin to form almost immediately from the time the joint is assembled - depending upon the specific alloys and conditions, who is to say how long or short it will be until the relatively minor gripping points between the AL and FE alloy are degraded by this nearly invisible corrosion and allow slippage of the joint. Another issue you are creating is that of thermal change between the dissimilar metals whereas not only aluminum or brass has a vastly different amount of shrink & growth associated with temperature changes so too does different alloys steel and even different lots of the same steel alloy. Take into consideration that the joint created between the steel receiver and aluminum block or brass pillars is only going to be compatible at that single temperature where the joint was created - thus if the joint was fitted in an ambient temperature of say 70F, the mating of that same joint will be vastly different at 60F as it will at 80F and the amount of difference increased with the differential in ambient temperature. Also, you have to contend with the changes in the mating surface connection points of the block/pillars to the stock not only with temperature changes but also with humidity and altitude pressure changes. Wood, composites and plastics vary dimensionally at different levels of atmospheric pressure. Lower pressures and higher temperatures allow the materials to expand more while higher pressures and lower temperatures cause more contraction.

Here are three point-plot graphs showing the difference in cumulative average vertical deviation in each direction ( 33 of the vertical centerline - 66 total) which does take into account the clipped portion not shown in the analog visual graph as well as the nominal frequency changes as indicated by the points being representative of the average maximum peak movement values as they relate to the relative static centerline of the bore as indicated by the horizontal centerline in the graph representing the differential of vertical change. The squares only indicate the position of the muzzle upon the projectile being no longer in contact with the barrel. The graphs show the cumulative average of five rounds fired, all using the same factory loaded ammo from the same box and all using the same exact off-the-shelf rifle & stock with the only changes being factory attachment of receiver to stock but ensuring complete free-floating of the barrel then full bedding with the respective compounds.









__________________
"Carry the battle to them. Don't let them bring it to you. Put them on the defensive and don't ever apologize for anything." ~ Harry S. Truman

Liberty is only assured as long government fears the people!

Last edited by markkw; 06-01-2008 at 06:02 AM.
Reply With Quote
  #5  
Old 05-31-2008, 09:00 AM
faucettb's Avatar
Beartooth Regular
 
Join Date: Feb 2004
Location: Peck, Idaho
Posts: 12,620
Boy Mark, you've got way to many big words for me. All kidding aside you bring to light some interesting points about bedding rifles. I've always wondered about the aluminum bedding blocks and the reasons for them.

When you glassbed a rifle your getting a cast in fit of the action and recoil lug into the stock. With the epoxy material bonded to the stock this makes for a really good fit of the action and barrel to the stock. I've never quite understood how machining an aluminum block that still needs bedded to a stock can in essence create accuracy over an epoxy glass bedded system.

Frankly I like the idea of piller bedding, but for years did it with acra-glass instead of metal pillers. When I glass bedded the floorplate I opened up the bottom half of the guard screw holes to a half inch or little better diameter and used enough glassbed material to fill those holes up. I then re drilled the guard screw holes from the top of the action. When I bedded in the action the top half of these holes were opened up and then bedded in with acra-glass. Acra-glass has a higher tensile strength than steel and I've always felt this made a better piller bedding system than steel or aluminum pillers that are glassed in anyway. I've seen on an average a 10 percent increase in accuracy from a glass bedded action and often much better. This from 27 years of gun smithing and near 40 years of bedding bolt action rifles.

Lets talk about free floating some. When I was helping with one of Speer's reloading manuals years ago I got to be part of some accuracy testing. Speer used a bunch of different rifles for velocity and accuracy testing instead of pressure barrels. We found that free floating and bedding in a barrel solid really didn't make a lot of accuracy difference until the barrel got above the four pound weight. From that point free floating gave better accuracy than solid bedded barrels.

Another think I've found is that if a barrel isn't delivering decent accuracy after it's free floated it almost invariably improved by putting around 7 pounds of upward pressure near the end of the forearm between the barrel and forearm.

When folks brought rifles into the shop for a glass bedding job I always ask if they wanted the barrel free floated, with pressure on the forend or glassed in solid. Figured the customer was always right, though I'd sure try to steer them to a method for that particular gun that I felt was going to deliver the best accuracy.

The harmonic vibration problem you brought to light sure can be a bugger at times and harmonic dampeners have appeared on the market over the years as Brownings and Winchester's BOSS systems and the new Limbsaver chunk of plastic rubber you slide on a barrel now. I do know that the BOSS system works very well, but haven't done anything with that ugly chunk of plastic that you slide on the barrel.

One thing I haven't seen is folks shooting bench rest competition using any of the barrel vibration dampener attachments on competition rifles. Perhaps that's simply a rule thing as I've been out of the bench rest thing since the late 60's.

There's some interesting barrel vibration studies on Varmint Al's site showing exactly what your talking about above Mark.

Anyway back to Ironworkers's original post, it may be that 3/4 inch groups are all his rifle may be capable of. That's actually pretty good accuracy from a standard weight varmint rifle. Bedding may help, but so may different bullet and powder selection. I've also found that fast twist barrels may also not be as accurate as a standard twist barrel in smaller calibers.
__________________
Bob from Idaho
Reply With Quote
  #6  
Old 05-31-2008, 09:40 AM
Beartooth Regular
 
Join Date: May 2008
Posts: 100
Question Thanks men for your expertise and time

I have a Rem 700 Sendero that has that Aluminum bedding block in it. But the only thing now that is Remington is the stock and the action. Chambered in 6x284 Hart Varmint BBL Jewell Trigger Extra heavy Recoil lug. I can get under half inch groups with that. Any how back to my Cooper.My best loads were Nosler 55gr BT in front of 39 grs of IMR 4064 . But I'd get too many frequent flyer's and more with the 75gr A-maxs. All bullets have to be seated into the lands. I just want better consistency. I know I can send a coyote into eternity now I just want the best for a 21st century rifle. I just wonder if I'm asking too much out of this rifle ? Oh and the muzzle diameter is .640 at the end........26" 8" twist cut rifled BBL. Any recommendations on who can do the right bedding job?
Reply With Quote
  #7  
Old 05-31-2008, 10:06 AM
faucettb's Avatar
Beartooth Regular
 
Join Date: Feb 2004
Location: Peck, Idaho
Posts: 12,620
Glassbedding is not a hard job and you can do it yourself. Most smiths that have been in business a while do a pretty fair job of bedding. If I were having it done I'd like to find a local smith so I didn't have to send it anywhere.

I'd check around locally and see if I could find someone near where you live to do it.

You may simply be asking more than that particular rifle can deliver and bedding it with any system may or may not give you a better shooting rifle. If you go to the tech department at Brownell's you can look up several articles that may give you some insight into the bedding processes. Here's the link to look at that.

http://www.brownells.com/aspx/NS/Gun...erarchive.aspx
__________________
Bob from Idaho
Reply With Quote
  #8  
Old 06-01-2008, 06:52 AM
markkw's Avatar
Beartooth Regular
 
Join Date: Dec 2004
Location: FL
Posts: 1,946
Bob,

I've been at this for less time than you have, the first rifle I bedded was a Savage 110 in .243 and that back in the 80's. I picked it up used but very little, it wouldn't group well and I got talked into bedding it with Marine Bond, a hard setting marine epoxy that cost me a small fortune at the time - I remember it only because it was difficult to find and I had to order it through the local hardware store. I waited weeks to get it and when they finally called to say it was in, they didn't bother to note that the company sent them two cans of Part A. Weeks long I waited while I had to pay to ship one can of Part A back and receive the replacement can of Part B. That's when the real fun started because after mixing the two parts, had about the same viscosity as chicken broth. There was no keeping that stuff in the stock, I used fire clay I dug out on our property trying to seal all the holes to keep it from running out anymore than it already was. It took better than a week to cure, may have been near two weeks. When I was done, yes the rifle shot a little better with one particular load but the accuracy return was definitely nowhere near the effort and cost put forth.

I bedded several others over the years, some just the receiver, some just the barrel and all with mixed results. Of those where accuracy increased, most were extremely picky about the load they would shoot and it was "that load", "that powder" and "that bullet" or nothing at all.

Nine years ago when I bought a featherweight M-70 that wouldn't shoot nothing at all is when I really got into this. I knew there had to be an answer of some kind so I started looking. I poured over ever piece of information I could find on bedding and front-end up pressure. Then I started applying structural mechanical engineering theory since the barrel & receiver combination are nothing more than a simple cantilever problem ... at least to a point if the barrel is free-floated. Advancements in structural testing and design proved that seemingly minor resonant vibrations, such as those induced by rotating equipment, were actually the cause of several structural and equipment failures that had previously been blamed on faults of the construction process and/or faults in the manufacturing of the steel used. One such was a cantilever mezzanine that was seemingly over-built as it only supported a load that was barely 5% of its rated capacity however it came crashing down without warning killing a couple workers in a factory. Of course it lead to a wrongful death suit and the contractor was being blamed, his lawyer of course blamed the engineer who in turn blamed the steel mfg. It was the steel mfg that provided the proof that the resonant vibration created by the small 7.5Hp air handler fan resulted in the free-end of the cantilever having sufficient vertical movement created by the vibrations being amplified in the length of the cantilever span. In essence, without knowing it, the length of the cantilever beam just happened to be perfect to maximize the effects of the vibrations - somewhat like tuning a xylophone bar to proper length so as to produce a given tone frequency.

Okay, so what the heck does a fan on a mezzanine have to do with a rifle? Well, here's where it starts getting fun - but, I'm going to keep this brief.

For every action, there is an equal and opposite reaction. Thus, the movement of the sear released the hammer/firing pin, that movement sends vibration pulses through the receiver and into the barrel. Now, this isn't a one-time deal because since the vibration cannot terminate at the free-end of the cantilever (muzzle), they act like a wave in a tub of water reversing and returning back to the source loosing a little energy (amplitude) in the reversal process. Just as in a tuning fork or the xylophone bar, this oscillation from end to end will continue until all the energy has been expended so these vibration waves will travel from receiver to muzzle and back again numerous times. While those vibrations are still in progress, the firing pin contacts the primer and another vibration frequency is induced into the assembly, as these vibrations pass the existing ones, they act upon each other, sometimes adding or subtracting energy and sometimes one will ride over the other as I alluded to in the previous reply of the small ripples in the water riding on top of the larger ones. Then the primer fires and now you not only have the addition of vibration pulses but the ignition of the primer and subsequently the powder cause rapid changes in the pressure contained within the chamber - this now creates annular pressure waves that to will travel end to end just as the vibration pulses.

A few things you have to understand is that the longitudinal (end to end) speed of sound in steel is roughly 5960 m/s or 19,554 fps - there is variations in the speed proportional to the particular alloy and the temperature of the alloy. The transverse (perpendicular to the length) speed if sound through steel is roughly 3240 m/s or 10,630 fps (same variations as above apply here as well). In a free-floated assembly, there is very little transverse action to consider since there is nothing essentially acting upon the barrel plane however one can quite effectively argue the point of sound waves emanating from the barrel being reflected by close proximity of the fore stock resulting in transverse actions but for the sake of simplicity we'll just ignore them for now. Considering only the longitudinal actions, the muzzle can be moved easily anywhere in a 360 position around it's nominal accepted plane relative to the bore in a static condition - in other words, it's going to stay put until sear trips and things start happening in the receiver that cause the muzzle to move. In tuning a load for a free-floated barrel, you are doing nothing more than attempting to time the bullet leaving the bore so that the muzzle is relatively close to the same position with every shot. That's all fine and dandy...if it works to your satisfaction.

Now, if we look at the condition where a point is created near the forward end of the stock that is putting upward pressure on the barrel, now we open a whole new can of worms, several cans actually. Now you have put not only a support under the cantilever but a non-anchoring support which the barrel is free to lift off of at will. You also created a point at which you now compound the movement created by the vibration pulses and pressure waves into two separate sections what will act in opposite directions yet they are connected to a common carrier being the barrel. Without getting into the lengthy reasons as to why (compound actions over a pivot), the results of this condition will most often lead to creating a rifle that will place two or three rounds fairly well at a given time and place but then will be iffy at other times or the "occasional fliers" are often more "occasional" than one would like. Another thing is, this configuration is what quite often leads to POI changes over time where you can zero the rifle with a given load now and put it away until next deer season and using the same load, the POI will be slightly different than what it was the year before simply because the constant pressure on a single point will induce stress into the barrel as does the constant hammering of that point with each round fired because the small support point is acting as an anvil and the barrel on either side of that point is trying to bend around it. Also you will often notice POI/accuracy changes when the ambient conditions change as well since the propagation of vibration pulses and annular energy waves change directly proportional to the ambient temperature, humidity and atmospheric pressure.

When you apply hard bedding (glass/metal) you're limiting the amount of movement in the direction towards the bedded side. As I alluded to above, now you have the condition created where the coin dropped into the kitchen countertop bounces and vibrates until it finally expends all its energy. The metal barrel sitting on top of the hard bedding compound acts the same as the metal coin hitting the hard countertop - neither surface "gives" and the result is that the vibration and pressure wave energy being transmitted through the barrel is forced to act more in one direction than the other because it's simply being reflected by the hard bedding. If you look at the "Hard Bedding" graph above (in my previous reply) note the considerable frequency and vertical movement increase as compared to the graph showing the free-floated results. Note the 12 point jump in the positive deviation value however this being the cumulative average over the 33 total travel arc referenced to the vertical centerline of the bore. The frequency increase caused by the vertical reflection being the key since the average deviation value changed very little despite the increased vertical deviation, the result being that it is more likely the bullet will exit the bore when the bore is closer to the same point each time simply by increasing the odds the muzzle will be transitioning the same point more often.

Now look at the considerable difference in values for flexible bedding (Ultra-RVC) that acts like the coin being dropped onto the towel, the coin's energy is absorbed by the towel, the same applies to a barrel. As opposed to reflecting energy back into the barrel, the flexible bedding absorbs the energy reducing both frequency and amplitude just as the towel absorbs the coin or a hand placed on a guitar string stops it from vibrating by absorbing the energy. Likewise, where the annular pressure waves force the barrel away from the hard bedding because the bedding cannot conform to the dimensional change, the flexible bedding absorbs energy by allowing the wave to displace the bedding which requires energy and thus drains energy from the barrel. Look at it this way - say you have a four wheel dolly loaded with 4000 pound block of iron on it. What will be the difference between rolling the loaded dolly over a 1" wide gap in the concrete floor if the dolly is equipped with 8" solid steel wheels and if it is equipped with 8" pneumatic tires? Of course, anyone who has ever moved anything mounted on solid steel or plastic castors knows full well a crack in the floor will cause a severe shock to be transmitted from the hard wheel into whatever its attached to. Likewise, loads mounted on pneumatic tires absorb the energy induced by the shock of the wheel dropping into the crack and very shock or vibration makes it into whatever the tire is attached to.

Think about it...why an airbag in you car instead of an anvil to catch your head in a crash?
__________________
"Carry the battle to them. Don't let them bring it to you. Put them on the defensive and don't ever apologize for anything." ~ Harry S. Truman

Liberty is only assured as long government fears the people!

Last edited by markkw; 06-01-2008 at 07:01 AM.
Reply With Quote
  #9  
Old 06-01-2008, 10:12 AM
Beartooth Regular
 
Join Date: May 2008
Posts: 100
Thumbs up Tons of Facts

Markkw Thanks for your time and effort in your post.I've never removed the stock from my Cooper .I've been told by another that at the recoil lug its been bedded at factory. This is my walking predator/varmint rifle. I can get 3/4" MOA out of it with frequent fliers all with in a head shot on a coyote at 100 yards . I must consider cost and actual benefit in relation to the purpose of this rifle.Local gun smith says he'll piller bed it ( His bedding is a combo of glass bedding and piller bedding now if that also included hard bedding, like your talking about I'll have to ask him) for about $200 bucks . That's quite expensive for some thing that might not improve what I'm already getting plus, that's enough for a weekend get away.

Last edited by Ironworker; 06-01-2008 at 10:17 AM.
Reply With Quote
  #10  
Old 06-01-2008, 11:15 AM
faucettb's Avatar
Beartooth Regular
 
Join Date: Feb 2004
Location: Peck, Idaho
Posts: 12,620
boy I've been out of the business for a while. I used to charge 35 bucks for a glass bed job and that included piller bedding, at least the style of piller bedding I used. If cooper glass bedded the recoil lug I'm doubting that your going to get a bunch of improvement in accuracy over what they've already done to the stock and I sure can't see a $200.00 improvement.

I'd ask to be sure, but usually what you get for a glassbed job is the action and recoil lug and the first inch or two of the barrel glassed in. Some smiths also bed in the floorplate. Piller bedding consists of opening up the holes thru the stock where the action screws go thru and installing metal pillers bedded or glued in with acra-glass or the smiths choice of epoxy bedding materials. The stock screws go thru these pillers and don't allow tightening of the action screws to compress the stock. This is supposed to give a consistent tork on the action everytime.

I'd probably leave it as is unless your competing in some kind of event that would require better accuracy.

I would check to see if the barrel is free floated. That's a simple test, just run a dollar bill down the barrel channel between the barrel and the stock. It should go almost all the way to the action.







If you can't do that just take the barreled action out of the stock and using a socket or a dowel about the size of the barrel channel wrapped in sandpaper sand it out til you can. Be sure to use some stock finish such as Birchwood Casey's Tru oil to seal the places you sanded. That might help with the inconsistency's and drop your group size some.
__________________
Bob from Idaho
Reply With Quote
  #11  
Old 06-01-2008, 09:00 PM
markkw's Avatar
Beartooth Regular
 
Join Date: Dec 2004
Location: FL
Posts: 1,946
Ironworker,

I didn't mean to be confusing - by "hard bedding" I mean any of the hard-set epoxies like Devon, Acraglas, Liquid Metal, ect. These are all epoxies that cure to a rock-hard condition. Ultra-RVC is flexible in that it cures to the consistency similar to that of a standard O-ring, it has give and flexibility that allows it to absorb energy rather than just reflect it.

If you're getting 3/4"@100, I'd try tweaking the load a little more and see if you can't cure the fliers. Just curious, do you check the weight of the bullets and have you tried a different brand of bullet in the same weight and style?

The info I posted on the bedding didn't really apply to this particular gun but since you asked about it.... it's one of my things, I put seven years into R&D and I do tend to get carried away at times, what can I say, I like broken thing - if they work right, they're boring because there is no challenge to overcome.

BTW, is that stock you have vented? C'mon man, ask about venting would ya?

Being a hammer slammera and rod burner myself, what kind of iron work is it that you do?
__________________
"Carry the battle to them. Don't let them bring it to you. Put them on the defensive and don't ever apologize for anything." ~ Harry S. Truman

Liberty is only assured as long government fears the people!
Reply With Quote
  #12  
Old 06-01-2008, 09:03 PM
markkw's Avatar
Beartooth Regular
 
Join Date: Dec 2004
Location: FL
Posts: 1,946
Bob, You need to pile stuff on top of that chest freezer ... a flat surface not loaded with crap in a workshop will lead to some questioning your manhood! LOL
__________________
"Carry the battle to them. Don't let them bring it to you. Put them on the defensive and don't ever apologize for anything." ~ Harry S. Truman

Liberty is only assured as long government fears the people!
Reply With Quote
  #13  
Old 06-01-2008, 09:11 PM
Beartooth Regular
 
Join Date: May 2008
Posts: 100
Thumbs up For moral reason I'll not own a vented Stock.

I'm a structural union Iron Worker who would never vote democrat ever. I work on bridges and High rise structures or any where structural steel is being erected or rigging is involved. I shot Sierra 55gr Blitzkings and so far Noslers are the best. Hornady 75gr A-maxs were inconsistent. Now the people who installed my new BBL and did a bad job of dura coating. ( I sent it back) plus complained about accuracy. They said the stock was touching and they shaved the stock fix it. So I'll try my same loads. They said their bbls shoot faster then others. I can get 3900+ with 39grs of IMR 4064 and bullet seated into lands.I don't want to experiment to much because in the process I might shoot the BBL out. I want to send a coyote in to eternity . So Markkw where do you burn rod at? I'm in the SF Bay area where the worst guns laws exist?
Reply With Quote
  #14  
Old 06-01-2008, 09:12 PM
faucettb's Avatar
Beartooth Regular
 
Join Date: Feb 2004
Location: Peck, Idaho
Posts: 12,620
Mark your a man after my own heart. I'm not going to show any pix of my work benches.

Ironworker if I were going to use a soft bed product as Mark suggests I would use it under the action and barrel, but hard bed the recoil lug and pillers, if you were to use pillers, in with an epoxy bedding material. I like Brownell's acra-glass, but there are several good glass bedding products on the market.
__________________
Bob from Idaho
Reply With Quote
  #15  
Old 06-01-2008, 09:16 PM
Beartooth Regular
 
Join Date: May 2008
Posts: 100
Thumbs up Not in any hurry to dump more $$$$$

Shooters you all have been a huge help to me in my time of need. I'm wishing you all a great work week. If it arrives back from BBL maker ( after fixing his screw up) I plan to shoot it this weekend. Thanks Men
Reply With Quote
  #16  
Old 06-02-2008, 03:24 AM
markkw's Avatar
Beartooth Regular
 
Join Date: Dec 2004
Location: FL
Posts: 1,946
Ironworker,

I burned rod for myself, I used to build custom equipment for mines, manufacturing and waste oil businesses in addition to doing some structural work in PA. When there was no building work to be had, I did repair work - there was never a shortage of things to do. I had to stop doing that work in 2005 when the existing injuries to my knee and back from 20 years ago finally took their toll on me. I got up one day feeling like I had a knot in my back and by 2am the following morning I couldn't walk and was in the worst pain I had ever felt. The only way to describe it is if you can imagine what it would feel like to have someone peel all the meat the inside and front of your leg as well as your groin using a chainsaw and taking their time about it - not fun especially considering it went 24/7 like that for 14 months. The extreme pain backed off but I'm still in a lot of pain and the cramping is something fitting of a torture chamber. So, it caused a major change in my life and the most important advice I can give you is to take care of your body because you have no idea how painful a simple sneeze can be.

I'd give that rifle a try again and see what she does and if things are no different, I'd try going down/up a little with the load depending on where your at with it now, sometimes just adjusting the velocity even a small amount either way will make a big difference in accuracy because of timing. Another thing is every powder generates its own unique vibration/pressure wave signature in the steel thus pushing the same bullet with powder "D" as opposed to powder "B" will also make a big difference. If you see a consistency in the inconsistency, that's when you know for fact that you have something going on that needs attention.

Bob said about the barrel eggs, those rubber egg looking deals you slide over the barrel. While these things are far from being a cure for anything, they can be a helpful troubleshooting tool and of course you don't need to buy one just to try one time. I know you have an old pair of welding gloves around, cut the leather cuff off one into a strip about 2" wide, wrap it around the barrel tightly just forward of the stock and secure in place with some electrical tape. See what happens to your group then move it halfway between the stock and muzzle and shoot another group. If you see a definite change in the group size when adding the snubber or moving it, then you will have some information on which to begin figuring out the problem(s). FYI, don't shoot a lot of rounds quickly with the leather wrap on the bbl so you don't overheat that one spot and warp it.

(all pic's taken in PA)
Working on the small hoe at one of the coal mines



Inclined in-feed screen & sump at a fine coal processing plant I built.




Some shop work for Bob



__________________
"Carry the battle to them. Don't let them bring it to you. Put them on the defensive and don't ever apologize for anything." ~ Harry S. Truman

Liberty is only assured as long government fears the people!

Last edited by markkw; 06-02-2008 at 03:35 AM.
Reply With Quote
  #17  
Old 06-02-2008, 03:47 AM
markkw's Avatar
Beartooth Regular
 
Join Date: Dec 2004
Location: FL
Posts: 1,946
Bob,

The soft bed works on the action too because unless the action requires tiling to remove from the stock, you don't have to allow any clearance around the recoil lug because the bedding has some "give" to it, it'll snap into place. It's also done with an interference fit so that you allow the bedding to cure with the barrel and/or action 0.003"-0.008" higher than it's fully seated position then after the bedding cures, you remove the spacers and draw everything down into the bedding so everything maintains 100% positive contact at all times regardless of minor differences in stock growth or shrinkage.
__________________
"Carry the battle to them. Don't let them bring it to you. Put them on the defensive and don't ever apologize for anything." ~ Harry S. Truman

Liberty is only assured as long government fears the people!
Reply With Quote
  #18  
Old 06-02-2008, 05:46 AM
faucettb's Avatar
Beartooth Regular
 
Join Date: Feb 2004
Location: Peck, Idaho
Posts: 12,620
My only concern with soft bedding the recoil lug would be that the recoil wold allow the barreled action enough movement that the tang would crack the stock at the wrist. I've repaired a bunch of stocks that were un-bedded that cracked because the recoil lug had enough clearance that it allowed some movement rearward. In a tightly inletted stock it doesn't take much movement to crack a stock at the wrist or behind a tightly fitted guard screw.

All the force from the recoil lug gets concentrated in the wood (speaking of wood stocks) behind that recoil lug. It's one place where it would seem that any flex is going to translate that force (recoil) being placed in the stock somewhere else. That somewhere else usually is the tang of the action and will crack a stock.

Most of the custom rifle companies that stock in wood and even synthetic bed this one point in for just that reason. Given I've never tried a soft bed compound this is speculation on my part, but I've had a bunch of broken stocks go thru the shop that though un-bedded cracked in the wrist just because of a few thousands movement of the action behind the recoil lug.

I don't see any problem using soft bed under the action and barrel, but I'd still probably use some acra-glass behind the recoil lug. I'm going to have to try that out. One of the reasons I quit using Acra-gel was it appeared almost rubbery to me after it had set up. Perhaps Brownell's is on to something with that formulation.
__________________
Bob from Idaho
Reply With Quote
  #19  
Old 06-03-2008, 07:07 AM
markkw's Avatar
Beartooth Regular
 
Join Date: Dec 2004
Location: FL
Posts: 1,946
Bob,

Yes, there are two ways of doing it ... if you soft bed, you need to relieve all binding points and allow the action clearance to move as much as you allow for with the recoil lug bedding. IE: if you bed the lug with say 0.015" thick bedding, you need to allow at least 0.020" clearance in the rearward direction or maintain the same bedding across the spectrum as such opening screw holes and any other place that would become an inadvertent a transfer/impact point. If flex bedding the lug, you are effectively floating the receiver & barrel assembly somewhat independent of the stock however, the allowance of movement must be limited to that which allows only for reduction of the initial shock loading as too much movement can cause all sorts of issues. The design of the gun is the most important determining factor as to if you can soft bed the action or not since there are those where attachment points to the stock exceed reasonable modification measures - in these cases, a hard bedding is the optimum choice for the recoil areas. (Common sense engineering goes a long way in determining the best option for each situation - nothing is "one size fits all")

Here's an example of a very simple total isolation with soft bedding. This is a Marlin 25N, obviously the only attachment point is the single screw at midship. It's a little hard to see but there are bedding pads at the rear of the action, the central one between the trigger hole and mag hole and of course on the columns between the vents under the bbl. The dark ring around the anchor screw hole is the spacer washer used to set the desired bedding thickness - also note the small rectangular hole in the between the trigger & mag holes, that is where a second thickness spacer was glued to the receiver. Once this portion of the bedding cured, the barreled action is held into position by temporary binding (I use cotton washline rope so it doesn't bugger the wood or metal finish) the anchor screw was removed and a small amount of addition bedding compound was allowed to fill in around the threaded anchor lug the screw goes into, when cured, this surface than absorbs the shock load allowing the entire action and barrel to be completely isolated from the wood. The anchor screw head is also isolated by cutting a recess into the wood under the screw head and creating the same thickness of bedding under the head as is under the action (I allow for using a metal washer under the screw head to keep the head from scrubbing on the bedding when installing/removing it.



Prior to final assembly, the spacers are removed so that when the action is set into the stock, the screw will pull everything securely into the bedding so that there are no contact points other than to the bedding. Clearly the time I put into this little .22lr was a bit excessive but it makes for a nice little sample piece. Although this rifle shot decent as in 1.5" @ 100yds with S&B standard velocity 40gr, after the bedding was done it now holds just under 1" @ 100yds (c-c measure) with the same ammo.

One thing that is often overlooked is the ability to maintain consistent pressure on the action no matter if you choose to bed the bbl or not. When the recoil lug is hard bedded, you need to allow clearance for disassembly and this means you can still have movement between the lug and bedding no matter if the bedding is of a compound or metal. As I mentioned in the earlier post, changes in temperature, humidity and atmospheric pressure can all have pronounced affects on any connection point. When it is possible to completely isolate the the metal parts from the stock with the flex bedding, you eliminate most of these concerns because the "give" in the bedding allows for these minor variations which hard bedding cannot because it's size is fixed.

Like I said, there's no "one size fits all" answer to anything and anyone claiming such is simply ignorant of the facts or intentionally trying to defraud you. Every single gun is an individual unto itself and while one can offer suggestive guildlines as to the application of a product like bedding, be it hard or soft, yet the final answer is going to come from the combined knowledge of the person doing the work as well as the direct feedback from the individual gun.

I use Ultra-RVC on muzzleloaders bedding the entire length of the barrel on most. During the cure, I use spacers under the bbl and remove them once cure is complete, when the bbl is re-installed in the stock, the bedding provides a slight tenstion between the wedges/pins and the stock - result is not only absorbing vibration for improved accuracy but it also eliminates the slight movement between the connection points that lead to them loosing-up over time. I've also used the soft bedding inside handguards on single shot rifles, even though the screw/spring attachments were tight, they still allowed a tiny bit of movement that all adds up to potentially reducing accuracy. No matter where the soft buffer material is applied, it will help reduce the vibration effects on the barrel, just as you can place your finger anywhere along the lenght of a guitar strings and muffle its sound by letting your finger absorb the vibration energy, so too can the vibration within a barrel be reduced.
__________________
"Carry the battle to them. Don't let them bring it to you. Put them on the defensive and don't ever apologize for anything." ~ Harry S. Truman

Liberty is only assured as long government fears the people!
Reply With Quote
  #20  
Old 06-03-2008, 08:13 AM
faucettb's Avatar
Beartooth Regular
 
Join Date: Feb 2004
Location: Peck, Idaho
Posts: 12,620
Mark

What an interesting conversation on bedding. I've never spent much time thinking about bedding low recoiling rifles such as 22's. Mostly centerfires, either hard recoiling big game rifles or mild recoiling varmint and bench rest rifles looking for accuracy. Have to say I've just never considered soft bedding materials and that's a novel thought.

There is some interesting info on bedding rimfire's, specifically the CZ 452's here. Skip down to the FAQ section for that.

Eric Brooks - Accessories for the CZ 452

Over the course of near 40 years of glassbedding rifles I've always bedded the recoil lug in solid with no clearance measures. This is the one place where you want an interference fit. At least it seems so to me. The big reason for this "cast in fit" is to keep the barreled action from any movement when fired or to transmit any movement to the whole barreled action stock system. Separating them was a major reason for both stock failure (cracking) or less than desirable accuracy.

The idea behind this was to make the action fit as solid as possible to the stock, i.e. to make the barreled action and stock seem to act as one piece. Solid bedding with the action, recoil lug and barrel, to some extent, cast in place in the epoxy substrate did this.

This worked well, but sometimes barrel vibrations still caused some groups to open up. This often could be cured by floating the barrel off of the stock from the action just in front of the recoil lug or a few inches ahead to the end of the forearm. This let the barrel just vibrate as much as it wanted to. When this still didn't help then rifle makers began using a bedding block with some upward pressure at the end of the forearm. Most found that about 7 pounds of pressure seemed to work best.

Bedding with materials that allow movement of the barreled action is a novel idea and one that I've not explored. I've always got exceptional accuracy from hard bedded guns so haven't done anything with any other bedding techniques. Most gunsmiths I know and even Brownell's in their years of servicing gunsmiths have little or no information on soft bedding materials. I would suspect one of the reasons is that on high recoiling rifle/cartridge combinations stock damage might be a problem.

The rubber donut now being offered as a vibration damper is completely different than the metal weight dampers previously used. Here's what Varmint Al's site was using to effect barrel vibration problems and accuracy.

http://www.varmintal.com/aeste.htm

The Rubber donut now offered behaves much more like Mark's example of placing your finger on the barrel or soft bedding a barrel in than a weight that is adjustable on the end of the barrel that allows tuning a barrel for different loads and bullets.

Really nice pix of what you did in that stock. is the material under the barrel some kind of stick on material or is it the same soft bedding used under the action?

Anyway what a great discussion. Mark I sure like the metal work your doing. I've got a little workshop at home and bought a new MIG welder a few years ago so I could do some of the stuff I wanted to do when I retired. I've got a cutting torch, a 40 ton press, a 16 ton pipe bender and a 40 inch roll, shear and brake that will do up to 18 gauge metal.

My first project was a lead sled and shooting bench and I buggered it pretty badly as I didn't get enough gas flowing to properly cover the weld. It's still sticking together, but the welds look nasty. I'm doing better now though. Plan on building my own garden tractor/mower the next couple of years and I'm putting a 4.3 liter Chev v-6 with the 4 speed overdrive tranny in my little Suzuki Samari this summer.

It had been years since I had done any welding and then with an old stick welder, boy that mig outfit sure is slick.
__________________
Bob from Idaho
Reply With Quote
Reply

Thread Tools
Display Modes Rate This Thread
Rate This Thread:

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are On
Pingbacks are On
Refbacks are On


Similar Threads
Thread Thread Starter Forum Replies Last Post
My Marlins with Vintage Glass Swampman Big-Bore Lever Guns 2 03-27-2008 03:20 PM
Alternate synthetic bedding Ekoch424 Gunsmithing 6 01-06-2008 01:38 PM
Glass bedding synthetic stocks? RifleFan Gunsmithing 15 10-29-2006 12:43 PM
glass bedding grizzly Gunsmithing 8 01-19-2005 11:44 PM
glass bedding the mini14 tarheel catfish Gunsmithing 1 10-29-2003 05:27 AM


All times are GMT -8. The time now is 09:39 PM.

< Contact Us - Shooters Forum - Archive >

 
 

All Content & Design Copyright © 1999-2002 Beartooth Bullets, All Rights Reserved
View Privacy Policy | Contact Webmaster | Legal Information
Website Design & Development By Exbabylon Internet Solutions
Powered by vBulletin® Version 3.8.7
Copyright ©2000 - 2014, vBulletin Solutions, Inc.
SEO by vBSEO 3.6.0 PL2