Max COL Muzzle Gage, Home Made - Shooters Forum
» Advanced

Go Back   Shooters Forum > Handloading > Handloading Procedures/Practices
Register FAQ Members List Donate Calendar Search Today's Posts Mark Forums Read



Like Tree6Likes
Reply
 
LinkBack Thread Tools Rate Thread Display Modes
  #1  
Old 02-15-2012, 06:06 PM
cvc944's Avatar
Beartooth Regular
 
Join Date: Oct 2009
Posts: 168
Max COL Muzzle Gage, Home Made


Registered Users do not see the above ad.


Forum member StretchNM recently posted a way to obtain the maximum COL length for a given bullet in a given rifle as measured from the muzzle. He mentioned that this had been kicked around and pondered some, but there were issues that needed to be addressed. I liked the idea enough to pursue a way to do it.

Success! I just made a small, inexpensive, 7-piece kit that will work on rifles from .22 to .35 caliber. (It would be easy to add to the kit to go smaller and larger). It consists of 2 nylon spacers with thumb-screws, and 5 different brass jags. The nylon pieces and the thumb-screws were only $3.57 at Lowes. The brass jags I can't re-call, but the price was low enough that I forgot what it was. All of the pieces are made to fit a 1-piece cleaning rod. My rods are stainless steel made by Kleen-Bore. The ID of the nylon spacers were drilled out to slide snugly on the cleaning rod. A small 6-32 thumb-screw locks it against the rod so it doesn't move. The one spacer measures exactly 1.00" long. The other is about a half inch long. The jags were ground flat on the ends.

The first thing to do is measure from the bolt face to the muzzle. Slide the 1.00" collar onto the rod, then screw on the appropriate jag behind it. Slide the rod into the bore until it contacts the bolt face. Slide the collar down to the muzzle, then set the thumbscrew.

Second thing is to measure from the tip of the bullet to the muzzle. Take a bullet and barely seat it into an empty, un-sized case. Now use the bolt to slide the cartridge into the chamber until the bullet stops against the lands. Continue pushing the bolt to slide the case onto the stopped bullet. Close the bolt. Now, unscrew the jag, slide the short collar onto the rod, then screw the jag back in. You now have both collars on the rod. Insert the rod into the bore and slide it down gently until it rests against the tip of the bullet. Now slide the short collar down, then set the thumbscrew. Pull the rod out.

Third thing is measurements. Measure the distance from end to end of the spacers, deducting 1.00" - the length of the first spacer - to get your maximum COL. You may get a measurement of say 2.715". You know that if you want to be .015" off of the lands, you would load your cartridge to an over-all length of 2.700". I know that this is just a different way to do something that can be done in other ways. Of course the real beauty of it is that it keeps me off the streets and out of trouble.
LarryLee and SMK-1000plus like this.
Reply With Quote
  #2  
Old 02-16-2012, 04:21 AM
Beartooth Regular
 
Join Date: Jan 2012
Location: NE PA
Posts: 304
Sounds very interesting and I like the price for sure. However, I guess I am a mechanical nit wit because I have no idea what any of those parts are. I have an idea but it would take me forever to find them at Lowe's. Do you have the parts numbers at Lowe's or could you upload a picture?
Reply With Quote
  #3  
Old 02-16-2012, 12:23 PM
Beartooth Regular
 
Join Date: Sep 2009
Location: Mooresville, IN
Posts: 11,926
That sounds like a simple way of making sure your measurements are precise, CVC. This would make a great sticky, if you included some pictures and part numbers for guys to visualize it and know what to buy. Very cool of you to think of a way to improve the process!

The only thing I don't understand is why you would need more than maybe 2 or 3 jags? Are they meant to be caliber specific?
Reply With Quote
 
  #4  
Old 02-16-2012, 02:45 PM
Beartooth Regular
 
Join Date: Feb 2010
Location: Nebraska
Posts: 92
Nice job. I was thinking of trying the same thing after looking at Hornady's OAL gauge and what they wanted for it.
__________________
NRA Member
NFOA Member
Reply With Quote
  #5  
Old 02-16-2012, 04:06 PM
StretchNM's Avatar
Beartooth Regular
 
Join Date: Dec 2008
Location: Alamogordo, NM
Posts: 7,004
You did it, CVC! Outstanding. You need another picture or three though. If only one, then a pic of the two spacers, locked on the rod, with a set of calipers taking the final (less 1.0") measurement. I like it better than the wooden dowel and I think I'm going to do it exactly like you described.

Jason's right: this would be a good sticky.
__________________
Stretch

- "A people that elect corrupt politicians, imposters, thieves, and traitors are not victims, but accomplices" - George Orwell

- "In an age of universal deceit, telling the truth is a revolutionary act" - George Orwell

- "If you contribute something, you don;t contribute enough. If you contribute nothing, you receive everything." - Andrew Wilkow

DON'T BE SCARED
Reply With Quote
  #6  
Old 02-16-2012, 08:24 PM
Beartooth Regular
 
Join Date: Sep 2010
Location: NW NEW MEXICO
Posts: 155
Very well done CVC. I will be making one of these this weekend, as I see this as an essential (for me) piece of reloading equipment. This will be a big improvement over my old method. Thank You very much. Ron.
Reply With Quote
  #7  
Old 02-17-2012, 07:20 AM
unclenick's Avatar
Super Moderator
 
Join Date: Jan 2005
Location: Hilliard, Ohio
Posts: 12,088
I'll change the title of the thread to make it more descriptive, then stick it. This tool works on the same gaging principle as the Sinclair tool, except the Sinclair tool works from the breech end. Cvc944's is more economical, though, and I think it's easier to understand and use. It's a good idea. I suggest a series of photos showing each step on an actual rifle when you get time.


A couple of suggestions:

Gaging of most any kind is most accurate when practiced as a light contact sport. Rather than jam a bullet into the lands by seating a case onto it with the rifle bolt, simply hold the bullet against the lands with light finger pressure. A short length of <neck diameter="" wood="" dowel="" extending="" out="" behind="" the="" chamber="" is="" good="" for="" giving="" your="" fingers="" something="" to="" hold="" it="" with.="" you="" can="" also="" drill="" flash="" hole="" of="" a="" retired="" case="" this="" guide="" dowel.="" that="" will="" let="" set="" gage="" where="" bullet="" contact="" starts.="" some="" folks="" try="" jam="" bullets="" specific="" distances,="" like="" .010"="" into="" lands,="" and="" by="" using="" light="" they="" know="" need="" be="" longer="" their="" chosen="" engagement,="" wanting="" distance="" off="" lands="" shorter="" correct="" amount.="" if="" unknown="" at="" start="" process,="" won't="" exactly="" how="" far="" are="" when="" shorten="" col="" from="" what="" tool="" indicates.="" tangent="" ogive="" tend="" deeper="" than="" secant="" designs,="" further="" complicating="" issue.="" touch="" clears="" up.
wood dowel that extends out of the back of the chamber will let you do that. You can even drill out the flash hole on a retired, fired, but not resized case for the dowel to let the case serve as a guide. Chamfer the mouth if necessary so the bullet falls in and out of the neck.

The reason for the above is to establish where the bullet first meets the lands. Some folks intentionally load bullets to a specific jam depth, and they won't be able to calculate how much longer to make the COL to get the jam they want if they don't know the starting point of contact with the lands. Also, if you jam the bullet an undetermined distance into the throat at the start of the measurement, you won't know exactly how far off the lands are when you make the COL shorter. This is complicated by bullet design, as a tangent ogive, with its shallower contact angle, will jam deeper than a secant ogive does for a given amount of jam force. Light measuring contact clears these discrepancies up.

Pick your bullet. Many bullets designs have some variation in length. Sierra match hollow points, for example, can vary almost a hundredth of an inch within a box due to the way the point is formed. Go through your bullets and pick out several with some single, specific length to make the measurement and to adjust your seating die to match your desired bullet position. I would try to choose them as close to average as possible, but some brands will include bullets off different tooling, making that hard to do. Just picking a single length is the important part. When you set up your seater you usually tweak the stem down several times to get desired COL, but commonly then find the next bullet seated doesn't go in quite as far. That's because it's seated with a single stroke, giving the brass less time to relax and more chance to spring back, so you often find you have to adjust the seater a little deeper for your production run. This is why you want several bullets the same length so you can be sure you've got the seater adjusted where you want it.

Finally, you can maximize precision of the gage by being careful not to let the drill wobble when boring out the set spacers. Plastic can grab a drill and turn it a little. If you can, it's best to do the drilling on a drill press or a lathe to keep the hole as square to the ends of the spacer as practical. When you're done, put the spacer on the cleaning rod and spin it to check that the spacer ends don't wobble significantly. If they do, then you either want to do it over with new ones or you want to mark the points that will touch the muzzle, keep them aligned when you use the spacers, then measure only across those two points.

If you have a lathe, you can chuck the cleaning rod in it through the spindle bore, tighten the drilled-out spacer on it, then true the ends of the spacer in situ. That will change the spacer length you need to subtract, but you can measure it for that correction. The advantage is the contact and measuring points will be good all around. The cleaning rod, being smaller in diameter than the bores of most rifles will tend to lie at a slight angle, but the error is very small. Less than half a thousandth using a 3/16" rod in an 18" long .458" bore with a .45 cal rifle jag. Too small for the precision of the seater die and bullet-to-bullet tolerances to let you resolve it consistently. And that's the worst case. In an 18" .308 bore with .30 cal jag the error is only about a ten thousandth.</neck>
__________________
Nick
__________________________
Orange Hat Family Member
CMP Certified GSM Master Instructor
NRA Certified Instructor
NRA Benefactor Member
"First contemplation of the problems of Interior Ballistics gives the impression that they should yield rather easily to relatively simple methods of analysis. Further study shows the subject to be of almost unbelievable complexity." Homer Powley

Last edited by unclenick; 02-18-2012 at 08:28 AM. Reason: Typos
Reply With Quote
  #8  
Old 02-17-2012, 10:20 AM
Beartooth Regular
 
Join Date: Sep 2009
Location: Mooresville, IN
Posts: 11,926
...and we have a sticky!

Now it's time for step-by-step pictures to go along with the well-written instructions CVC already added.

I could see bundling the little collars and jags in 2 or 3 different sizes for the more common, commercially available cleaning rod diameters. As easy as these would be to make, I'd bet money guys would gladly pay for a small $7.99 kit that they use with the cleaning rod they already own.
Reply With Quote
  #9  
Old 02-17-2012, 11:44 AM
Beartooth Regular
 
Join Date: Jan 2012
Location: NE PA
Posts: 304
Sounds like that would be a good idea to sell the kit. Thanks for the picture as after seeing it I got what you were describing. I understood how it would work but had no idea what it would look like. Excellent idea an I am sure in no time at all there will be several clones being assembled after reading your description. Thanks.
Reply With Quote
  #10  
Old 02-18-2012, 08:39 AM
unclenick's Avatar
Super Moderator
 
Join Date: Jan 2005
Location: Hilliard, Ohio
Posts: 12,088
How about popping down to the hobby shop and getting a length of landing gear music wire that will fit through flash holes all the way to the bullet. 0.063" would work for all, and it's rigid enough for the job. If you want a handle for it, trim it to length with a Dremel cutoff wheel and put it in a pin vice (these are little handles with collets like a Dremel tool has). The Hobby shop may have those, too. If not, the cheap one at the top of this page would do.
__________________
Nick
__________________________
Orange Hat Family Member
CMP Certified GSM Master Instructor
NRA Certified Instructor
NRA Benefactor Member
"First contemplation of the problems of Interior Ballistics gives the impression that they should yield rather easily to relatively simple methods of analysis. Further study shows the subject to be of almost unbelievable complexity." Homer Powley

Last edited by unclenick; 02-18-2012 at 08:42 AM.
Reply With Quote
  #11  
Old 02-18-2012, 06:37 PM
unclenick's Avatar
Super Moderator
 
Join Date: Jan 2005
Location: Hilliard, Ohio
Posts: 12,088
Maybe I'm not quite getting your idea. Are you thinking to use a case as a bullet holder with the bullet just barely in its mouth? That might work out. The bullet will touch down on the lands before the case is all the way into the chamber, so in that instance any sized case, even a range foundling, should work. You could probably just curl your pinky finger into the chamber well enough to make the bullet touch the throat. If you have a deep bolt lug recess, like on my Styer, I bet any small flat screwdriver blade that fits inside the primer pocket but is wider than the flash hole will work, unmodified.
SMK-1000plus likes this.
__________________
Nick
__________________________
Orange Hat Family Member
CMP Certified GSM Master Instructor
NRA Certified Instructor
NRA Benefactor Member
"First contemplation of the problems of Interior Ballistics gives the impression that they should yield rather easily to relatively simple methods of analysis. Further study shows the subject to be of almost unbelievable complexity." Homer Powley
Reply With Quote
  #12  
Old 02-19-2012, 09:50 AM
StretchNM's Avatar
Beartooth Regular
 
Join Date: Dec 2008
Location: Alamogordo, NM
Posts: 7,004
I'm thinking the most accurate way to seat the bullet against the lands, is with the bolt removed. Whatever method used to hold the bullet in there (glued on the end of a dowel, seated long in a case mouth, etc.) is irrelevant, as long as you can be sure the bullet is seated against the lands.

Now, as far as bullet tips varying from one bullet to another within the same batch: the only way I can see to account for this is with something that will rest against the ogive, at some point along it's length, as opposed to the bullet tip. If you take a Lee bullet seater apart (or any bullet seat similarly constructed), you will find that the bullet fits inside of a floating "cone" that, hopefully, contacts the ogive of the bullet. Something similar to that, on the end of the aluminum rod, would do the trick. Some more math would be required, of course, beginning with determining, to an acceptable degree, just precisely where the point of contact is on the ogive. A tough job and more than I;m willing to contend with. Still though, measuring from the ogive as opposed to the tip will always be more accurate.

So, staying with measuring to the tip of the bullet and allowing for dented, malformed, and otherwise deformed tips, the first paragraph about bolt removal seems most accurate to me.
__________________
Stretch

- "A people that elect corrupt politicians, imposters, thieves, and traitors are not victims, but accomplices" - George Orwell

- "In an age of universal deceit, telling the truth is a revolutionary act" - George Orwell

- "If you contribute something, you don;t contribute enough. If you contribute nothing, you receive everything." - Andrew Wilkow

DON'T BE SCARED
Reply With Quote
  #13  
Old 02-19-2012, 01:07 PM
Beartooth Regular
 
Join Date: Apr 2004
Location: S.E. Lower Mich.
Posts: 942
Not sure what yer talking about Stretch. None of the methods wee've discussed use the tip to measure from. They are all measuring from the ogive, that is, the lead part of the ogive that first contacts the lands.
Reply With Quote
  #14  
Old 02-19-2012, 01:17 PM
StretchNM's Avatar
Beartooth Regular
 
Join Date: Dec 2008
Location: Alamogordo, NM
Posts: 7,004
Ok, sorry about that. Maybe a few posts went by that I didn;t read closely. I guess I missed the transition from square end of the measuring rod against the bullet tip to measuring to the ogive.
__________________
Stretch

- "A people that elect corrupt politicians, imposters, thieves, and traitors are not victims, but accomplices" - George Orwell

- "In an age of universal deceit, telling the truth is a revolutionary act" - George Orwell

- "If you contribute something, you don;t contribute enough. If you contribute nothing, you receive everything." - Andrew Wilkow

DON'T BE SCARED
Reply With Quote
  #15  
Old 02-19-2012, 02:13 PM
Beartooth Regular
 
Join Date: Apr 2004
Location: S.E. Lower Mich.
Posts: 942
Sorry, my mistake,
Reply With Quote
  #16  
Old 02-19-2012, 03:02 PM
StretchNM's Avatar
Beartooth Regular
 
Join Date: Dec 2008
Location: Alamogordo, NM
Posts: 7,004
Quote:
Originally Posted by cvc944 View Post
Nope, Stretch was right. We are measuring from the tip of the bullet. That is why unclenick cautioned on the differences in bullet overall lengths. If I change out a bullet with a different ogive, I just do it again. It's a quick and easy thing.
CVC, it really isn't the ogive that's accounting for different measurement. It's the tip of the bullet. If you look at a handfull of bullets, say Hornady Interlocks (just to pick one), you can see that some of the tips are deformed. Some are flattened while others are more pointed. I even had a bullet a couple of weeks ago that had a long hook of lead coming from the tip, and bent downward toward the base. Of course, with one like that, you spot it right away and twist it off, then decide if the tip is good enough to use and give an accurate measurement. I filed that one bad bullet tip to an acceptable tolerance, judging by eye. The difference between the tip of one bullet and the next could be several thousandths.

The ogive doesn;t change, as long as whatever tool you use to rest against it isn;t prevented from resting against the same place on all the bullets. It does affect where the bullet rests on the lands of the bore, but once a bullet is seated there, that's separate and apart from our measurement using the tools in this method. Of course, each brand, weight, and type of bullet we shoot has to be checked independantly. I write the absolute maximum OAL on the inside of the box lid, then deduct .020" and more to determine my true OAL.

I admit I use your method, albeit with wooden dowels instead of a more accurate jig that you've come up with. I just forgive the inaccuracies of the bullet tips. SInce I don;t think I've ever seated a bullet closer than .020" from the lands, I convince myself I'm on relatively safe ground. But.... I understand the maximum OAL I've come up with has some flaws in it's accuracy.
__________________
Stretch

- "A people that elect corrupt politicians, imposters, thieves, and traitors are not victims, but accomplices" - George Orwell

- "In an age of universal deceit, telling the truth is a revolutionary act" - George Orwell

- "If you contribute something, you don;t contribute enough. If you contribute nothing, you receive everything." - Andrew Wilkow

DON'T BE SCARED

Last edited by StretchNM; 02-19-2012 at 03:11 PM.
Reply With Quote
  #17  
Old 02-19-2012, 03:32 PM
Beartooth Regular
 
Join Date: Sep 2009
Location: Mooresville, IN
Posts: 11,926
Quote:
Originally Posted by StretchNM View Post
CVC, it really isn't the ogive that's accounting for different measurement. It's the tip of the bullet. If you look at a handfull of bullets, say Hornady Interlocks (just to pick one), you can see that some of the tips are deformed. Some are flattened while others are more pointed. I even had a bullet a couple of weeks ago that had a long hook of lead coming from the tip, and bent downward toward the base. Of course, with one like that, you spot it right away and twist it off, then decide if the tip is good enough to use and give an accurate measurement. I filed that one bad bullet tip to an acceptable tolerance, judging by eye. The difference between the tip of one bullet and the next could be several thousandths.

The ogive doesn;t change, as long as whatever tool you use to rest against it isn;t prevented from resting against the same place on all the bullets. It does affect where the bullet rests on the lands of the bore, but once a bullet is seated there, that's separate and apart from our measurement using the tools in this method. Of course, each brand, weight, and type of bullet we shoot has to be checked independantly. I write the absolute maximum OAL on the inside of the box lid, then deduct .020" and more to determine my true OAL.

I admit I use your method, albeit with wooden dowels instead of a more accurate jig that you've come up with. I just forgive the inaccuracies of the bullet tips. SInce I don;t think I've ever seated a bullet closer than .020" from the lands, I convince myself I'm on relatively safe ground. But.... I understand the maximum OAL I've come up with has some flaws in it's accuracy.
Since you're using the measurements you get as a starting point that you can work backward from, I don't think there are any flaws in the process. At least, no more so than the admittedly lesser flaws in OAL created by a conventional seating stem in your die. In the case of pointed bullets, we are seating to a certain depth by pressing against the ogive, or some portion of the bullet other than the tip. In this respect, the OAL of our loaded rounds can be only marginally more accurate than the measurement you would get from CVC's ingenuous tool design. If the uniformity of the tip is a limiting factor when using his new measuring tool, it would also be a limitation in getting a precise overall length from loaded round, wouldn't it?

In short: It's plenty good enough for any reloader who only needs that number for a reference so that he can seat ".xxx" deeper.
__________________
"My serious suggestion is to buy one rifle and then buy another one. And another." JBelk

Last edited by broom_jm; 02-19-2012 at 03:35 PM.
Reply With Quote
  #18  
Old 02-19-2012, 04:03 PM
unclenick's Avatar
Super Moderator
 
Join Date: Jan 2005
Location: Hilliard, Ohio
Posts: 12,088
CVC,

Re post #18,

The problem is the recess you cut in the jag to reach the ogive or any separate piece you might use then has to be used to somehow check that the seating die is correctly set to give you the right base-to-ogive length. That's the one thing that's tougher to do with your gage than with a Stoney Point type. Rather than complicate the measurement, I'd suggest you proceed as you have been until you assemble the first round to the correct length. Do that with the same bullet you used with the gage so you know its ogive is in the same place with respect to the tip (this is another thing that can vary a bit, bullet to bullet).

Once you have that assembled sample cartridge, get a metal spacer from Lowe's that your bullets won't quit fit through the hole off. You may have to drill one out, but you want to get as close to bore (not groove) diameter as you can without going over. Then just set that spacer on the bullet of the assembled sample cartridge and measure from cartridge case base to the far end of the spacer. Once you have that number, you can use it with the spacer to check the ogive positions of other bullets you seat.

You can also use the spacer with bullets by themselves to select ones with identical base-to-ogive dimensions to use in setting your seater die up, and not worry about COL after the first one.

The advantage of that method, if the hole in the spacer is close enough to bore diameter, is the dimension you find for the cartridge with spacer on top should then be pretty close to the same with other bullet shapes you use at that same distance off the lands. In other words, if you tried, say, three different shaped bullets with the gage, you'd get three different gage measurements for three different COL's. If you then assembled all three bullets into cartridges to match their respective gage numbers, even though they had different COL's, when you put the spacer on and measured from the case head to the far end of the spacer, the numbers would all be the same (within a few thousandths of the same). The RCBS Precision Mice depends on that principle as it has just one gage bullet profile it uses for all bullets.

So, you'd have one kiss-the-lands ogive length for all bullets as long as you used the same spacer with them all and as long as enough rounds hadn't gone down the tube to wear the throat forward. That's a number you'll want to check by re-gaging from time to time. In a medium power rifle cartridge it's probably enough to check every thousand rounds. In some of the throat burners you may want to check as often as every 100 rounds. You can always tweak your seating depths to chase the throat forward as it wears. Not sure how much difference that really makes, but it's one of those things one does because one can.
SMK-1000plus likes this.
__________________
Nick
__________________________
Orange Hat Family Member
CMP Certified GSM Master Instructor
NRA Certified Instructor
NRA Benefactor Member
"First contemplation of the problems of Interior Ballistics gives the impression that they should yield rather easily to relatively simple methods of analysis. Further study shows the subject to be of almost unbelievable complexity." Homer Powley

Last edited by unclenick; 02-19-2012 at 04:05 PM.
Reply With Quote
  #19  
Old 02-19-2012, 04:26 PM
StretchNM's Avatar
Beartooth Regular
 
Join Date: Dec 2008
Location: Alamogordo, NM
Posts: 7,004
Quote:
Originally Posted by broom_jm View Post
Since you're using the measurements you get as a starting point that you can work backward from, I don't think there are any flaws in the process. At least, no more so than the admittedly lesser flaws in OAL created by a conventional seating stem in your die. In the case of pointed bullets, we are seating to a certain depth by pressing against the ogive, or some portion of the bullet other than the tip. In this respect, the OAL of our loaded rounds can be only marginally more accurate than the measurement you would get from CVC's ingenuous tool design. If the uniformity of the tip is a limiting factor when using his new measuring tool, it would also be a limitation in getting a precise overall length from loaded round, wouldn't it?

In short: It's plenty good enough for any reloader who only needs that number for a reference so that he can seat ".xxx" deeper.
You're right, Jason, but I'm realizing there's a fix for it on the die end. The Lee seater die (as do others, probably) indexes on the ogive (of a spire point bullet). Using a Hornady Interlock spire point, for example, there is .142" clearance between the tip of the bullet and the inside top of the seater plug. So it is seating, with that particular bullet, on the ogive.

So, if we used the same bullet as was used in measuring the OAL, we could adjust the die to give a fairly accurate OAL for the remaining bullets, regardless of what the cartridges measured with calipers. There would be variations because of bullet tip deformation, but if we left the seater die alone after the initial setting, they would all measure the same where it counts. Even if we didn;t use the exact same bullet, as long as had earlier set it aside and then used a bullet with a similarly shaped tip, and that measured the same from base to tip, we could set the die with that bullet.

Maybe this was already a given to you fellows, and I really was missing that point earlier, like Jimbo said.
__________________
Stretch

- "A people that elect corrupt politicians, imposters, thieves, and traitors are not victims, but accomplices" - George Orwell

- "In an age of universal deceit, telling the truth is a revolutionary act" - George Orwell

- "If you contribute something, you don;t contribute enough. If you contribute nothing, you receive everything." - Andrew Wilkow

DON'T BE SCARED
Reply With Quote
  #20  
Old 02-20-2012, 08:18 AM
unclenick's Avatar
Super Moderator
 
Join Date: Jan 2005
Location: Hilliard, Ohio
Posts: 12,088
CVC,

Sorry about that. Looks like my brain started jumbling posts. It was actually Stretch that brought the ogive up, so that post would more have addressed his concern and describes how we'd work with your gage to wind up with an ogive referenced measurement. He is correct that bullet tips can be different distances from the ogive near the bullet shoulder where it actually contacts the lands. But there are other potential error sources as well. This is why I suggested that you work with an average length bullet. I should also have said to select average length (from head to shoulder datum) case for the seating depth adjustment. That way your errors will tend to be +/- around the average and that should normally keep you safe and still be good enough for match accuracy loads.

For case head to shoulder (case headspace fit) averaging, any comparative measurement will do. You don't need to invest in a gage for accurate absolute numbers to find an average. For that reason, you can improvise the case gage with a spacer, as I show below.

The actual length of the case below as SAAMI measures it, came out to 1.629". The number on the caliper is smaller because, even though I zeroed with the spacer between the caliper jaws and even though the spacer is sold as 3/8", its actual hole was 0.410" ID, plus it has a chamfered edge, where the SAAMI method requires a 0.400" hole for .308 cases and a sharp edge. So this measures shorter. Still, an average among cases measured this way will tend to be average among cases measured the SAAMI way, too. The only caveat is that it will be most accurate for cases shot in the same chamber the same number of times and resized in the same die at the same time so the setup is consistent.

Attached Thumbnails
Max COL Muzzle Gage, Home Made-poor-man-comparator-small.gif  
__________________
Nick
__________________________
Orange Hat Family Member
CMP Certified GSM Master Instructor
NRA Certified Instructor
NRA Benefactor Member
"First contemplation of the problems of Interior Ballistics gives the impression that they should yield rather easily to relatively simple methods of analysis. Further study shows the subject to be of almost unbelievable complexity." Homer Powley

Last edited by unclenick; 02-20-2012 at 08:21 AM.
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
The Carbon War Chronicles Humpy Gunsmithing 38 04-13-2017 11:01 AM
So my muzzle loader of a different flavor! tacklebury Muzzleloaders 14 10-13-2011 06:08 PM
Home made reloading/shooting accessories. Dean of Id Handloading Equipment 16 03-17-2009 07:46 PM
Italian Shotguns: Who Made These Two? NITRO Shotguns, Shotgunning, and Shotshell Reloading 0 03-03-2009 02:32 AM
Made Some Rammers Swampman Muzzleloaders 1 02-15-2009 06:02 PM


All times are GMT -8. The time now is 05:22 AM.

< Contact Us - Shooters Forum - Archive - Privacy Statement >

 
 

All Content & Design Copyright © 1999-2002 Beartooth Bullets, All Rights Reserved
Privacy Statement | Contact Webmaster
Website Design & Development By Exbabylon Internet Solutions
Powered by vBulletin® Version 3.8.8
Copyright ©2000 - 2017, vBulletin Solutions, Inc.
SEO by vBSEO 3.6.1