Joined
·
2,933 Posts
Is there a tried and true method for lapping the factory burs out of a new bore using JB Paste? Or should I just shoot and clean, shoot and clean? Thx for your input!
Hand lapping a new bore
1 - 20 of 49 Posts
Joined
·
13,162 Posts
There are break-in procedures, and cleaning with JB or Iosso Bore Cleaner will get them to progress a little better than just patches and solvent, but they don't truly lap the bore.
For true lapping you have basically two alternatives: hand lapping and firelapping. The first normally uses a lapping slug on the end of a cleaning rod that is cast into the muzzle of the bore by plugging the bore back an inch or two with patches or paper and pouring molten lead into it. Grooves similar to lead bullet lube grooves are cut into the cast slug with a knife or a gouge to hold abrasive compound. The lap is loaded (the grooves filled) with abrasive and run back and forth in the bore by hand. It's s common to use something like 320 grit silicone carbide lapping compound (Clover compound, for example). The slug is usually pure lead so that when it encounters a constriction it is narrowed and does not spring back out after passing through it. In this way all abrading on subsequent strokes is only in the tight spots. When you feel it stop cutting tight spots, you can bump the lap back up with a brass rod and hammer, and go at it some more. You keep repeating until the bore has no more tight spots and the lap feels smooth down the length of the bore.
The other method is firelapping. This involves shooting abrasive embedded bullets through the bore with very light loads that get low airgun velocities (300-500 fps). The lapping bullets are usually cast bullets in the hardness range of 10 to 12 BHN. This number range is a compromise. It doesn't limit itself to cutting constrictions as completely as pure lead laps on a rod, but it is malleable enough that it doesn't lap the wide places nearly as hard as the narrow ones. The reason it isn't pure lead is that where a pure lead hand lap can be pushed through a constriction by rod without bumping up, when you have even firelapping load pressures on the base of a pure lead bullet it will bump up to rub the wide spots as well as the narrow ones. At the other extreme, an alloy bullet of higher BHN is surprisingly elastic and will go tightly into the bore and stay tight all the way down its length, thorough narrow places and wide ones. That tends to remove material evenly everywhere. You don't want that because, while it widens tight spots, it widens wide places equally, so you don't level off major irregularities; you just smooth those shorter than the length of the slug. When you are done firelapping, irregularities are gone and it leaves the bore very slightly tapered down toward the muzzle. Maybe a half thousandth or so. This is considered desirable for accuracy, especially when the bore is to shoot lead bullets.
Either lapping method will reduce metal fouling, making the bore easier to clean. Firelapping has the advantage that in addition to introducing the slight taper, it also cleans the throat up. Hand lapping does not normally clean the tool marks off the throat because the rifling is cast into the slug when you pour the lap.
The board sponsor, Beartooth Bullets, sells a firelapping kit, here.
For true lapping you have basically two alternatives: hand lapping and firelapping. The first normally uses a lapping slug on the end of a cleaning rod that is cast into the muzzle of the bore by plugging the bore back an inch or two with patches or paper and pouring molten lead into it. Grooves similar to lead bullet lube grooves are cut into the cast slug with a knife or a gouge to hold abrasive compound. The lap is loaded (the grooves filled) with abrasive and run back and forth in the bore by hand. It's s common to use something like 320 grit silicone carbide lapping compound (Clover compound, for example). The slug is usually pure lead so that when it encounters a constriction it is narrowed and does not spring back out after passing through it. In this way all abrading on subsequent strokes is only in the tight spots. When you feel it stop cutting tight spots, you can bump the lap back up with a brass rod and hammer, and go at it some more. You keep repeating until the bore has no more tight spots and the lap feels smooth down the length of the bore.
The other method is firelapping. This involves shooting abrasive embedded bullets through the bore with very light loads that get low airgun velocities (300-500 fps). The lapping bullets are usually cast bullets in the hardness range of 10 to 12 BHN. This number range is a compromise. It doesn't limit itself to cutting constrictions as completely as pure lead laps on a rod, but it is malleable enough that it doesn't lap the wide places nearly as hard as the narrow ones. The reason it isn't pure lead is that where a pure lead hand lap can be pushed through a constriction by rod without bumping up, when you have even firelapping load pressures on the base of a pure lead bullet it will bump up to rub the wide spots as well as the narrow ones. At the other extreme, an alloy bullet of higher BHN is surprisingly elastic and will go tightly into the bore and stay tight all the way down its length, thorough narrow places and wide ones. That tends to remove material evenly everywhere. You don't want that because, while it widens tight spots, it widens wide places equally, so you don't level off major irregularities; you just smooth those shorter than the length of the slug. When you are done firelapping, irregularities are gone and it leaves the bore very slightly tapered down toward the muzzle. Maybe a half thousandth or so. This is considered desirable for accuracy, especially when the bore is to shoot lead bullets.
Either lapping method will reduce metal fouling, making the bore easier to clean. Firelapping has the advantage that in addition to introducing the slight taper, it also cleans the throat up. Hand lapping does not normally clean the tool marks off the throat because the rifling is cast into the slug when you pour the lap.
The board sponsor, Beartooth Bullets, sells a firelapping kit, here.
Joined
·
2,933 Posts
Thx for the feedback nick. The last new rifle I bought, a Stevens 200 in .30-06 shot like garbage for about 40 to 60 rounds. I got it at Bass Pro for $199 so I figured I just got what I paid for. Then on about the 3rd trip out, the groups tightened WAY up. It was a very nice surprise. It has shot lights out ever since. Does simpy shooting and cleaning well like this get the job done, or was I just lucky? Where is the best source for load data on the fire lapping?
Thx again!
Thx again!
Joined
·
36,072 Posts
Which one do you need load data for? I've used 4 grains of Bullseye in the .30-06, I can tell you a few other chamberings, but sounds like your -06 is working now, right?
You can sorta scale the loads from the example with .30-06 case. About 3 grains for a .35 Rem, perhaps 5 or so for a belted magnum, etc. It is somewhat rifle dependent and revolvers are pretty sensitive due to the variances in the b/c gap. 2.5 will do it for a .44 mag, and 2 might, depending on the gap. Marshall uses Red Dot with slightly heavier loads.
Stuffing the case full of polyester pillow fiber (dacron) on top of the powder helps a lot.
You can sorta scale the loads from the example with .30-06 case. About 3 grains for a .35 Rem, perhaps 5 or so for a belted magnum, etc. It is somewhat rifle dependent and revolvers are pretty sensitive due to the variances in the b/c gap. 2.5 will do it for a .44 mag, and 2 might, depending on the gap. Marshall uses Red Dot with slightly heavier loads.
Stuffing the case full of polyester pillow fiber (dacron) on top of the powder helps a lot.
Joined
·
2,933 Posts
Well this is for a .308. I have plenty of Green Dot and Blue Dot and a lil Red Dot. Plus some 700X. What happens to that dacron by the way on ignition?
Joined
·
13,162 Posts
I agree on the polyester fiber. If you use it in warmer loads, like cast bullet loads, it often just melts down to a fairly compact disk. Unlike using cereal fillers (Cream of Wheat being the old favorite) it has lots of air between the fibers so it doesn't take away a lot of the volume the gas needs to expand into. That's part of how cereal comes to cause chamber ringing. I've never heard of it occurring with Polyester. The stuff's dirt cheap at Walmart's sewing section, too.
Red Dot or 700X will work fine. Mike's load levels are fine for either one. The fiber, by keeping the powder against the flash hole, will also eliminate the very remote possibility of detonation from using such small charges. They are rare, but no point in leaving a door open when it's that easy to close.
Your Stevens sounds like a shooter. No reason it shouldn't be, as the Savage products are known for that. There could have been some crud in the barrel that blew out, but I doubt the shooting you did affected the barrel significantly. It is more likely it either settled the action in the stock or the bolt lugs found their center so they are now touching down more evenly.
Red Dot or 700X will work fine. Mike's load levels are fine for either one. The fiber, by keeping the powder against the flash hole, will also eliminate the very remote possibility of detonation from using such small charges. They are rare, but no point in leaving a door open when it's that easy to close.
Your Stevens sounds like a shooter. No reason it shouldn't be, as the Savage products are known for that. There could have been some crud in the barrel that blew out, but I doubt the shooting you did affected the barrel significantly. It is more likely it either settled the action in the stock or the bolt lugs found their center so they are now touching down more evenly.
Note of caution - the dacron or polyester filler is recommended. Cream of Wheat or similar grains ARE NOT recommended for bottleneck cartridges. The stuff will form a near solid core upon being compressed and will act like a plug when it hits the neck. Should only be used in straight walled cases.
Joined
·
2,933 Posts
I have a question about the action settling. The pillars in the stock are flat. The bottom of the action is rounded, so only about 3/16s" is making contact on each pillar lug. My gunsmith, who is an accomplished bench rest guy, pointed it out to me when I had him put in a heavier main bolt spring. It has allen screws on the main action bolts so I have them torqued WAY tight. Still, I am concerned that on horse back, or a four wheeler, or with recoil, the jostling around may cause slippage. It has held zero pretty well so far. I am considering an aftermarket stock anyway. If the one I get has pillars, I will just have the same issue wont I? What do you all suggest? The barrel obviously has a lot of accuracy potential. I hate to see it jepordized due to this poor contact issue. Or is the 3/16" that is contacting each pillar sufficient since I have it torqued very tight?
Joined
·
620 Posts
This is news to me. I have not done any cases with cream of wheat, but many of the bench guys that do it alot use that stuff! That's what I have read anyways. Wouldn't the polyester fibers melt in your barrel and cause some nasty "plastic" buildup in there?
Joined
·
13,162 Posts
B-D II,
You could build up bedding at the top side edges of the pillars to help cradle the action if you're having trouble with it? The deceptive thing is that for a given screw torque a wider support surface will have fewer PSI, so you are getting maximum compression of the aluminum now, and that may be the best friction? A pillar cradle arguably is best when the action doesn't quite bottom out, but is centered between two raised edges with a slightly undersized radius for the action contour. YMMV.
You could build up bedding at the top side edges of the pillars to help cradle the action if you're having trouble with it? The deceptive thing is that for a given screw torque a wider support surface will have fewer PSI, so you are getting maximum compression of the aluminum now, and that may be the best friction? A pillar cradle arguably is best when the action doesn't quite bottom out, but is centered between two raised edges with a slightly undersized radius for the action contour. YMMV.
Bird Dog 11 When I started cleaning up old barrels in 1975 all I could get my hands on was Colgate Tooth Powder. I'd use a tight fitting shotgun mop that had been wet then squeezed out and rolled in the powder. I'd do fourty strokes, clean the barrel, shoot three shot group, repeat until the groups got smaller. This is the only method that I've used all these years.
HI JUST NEW TO THE SIGHT AND DO NOT KNOW HOW TO POST A QUESTION COULD YOU PLEASE HELP Alvin Thanks
My e-mail is ####@####.###
(Edit note: You can email board members through the board by clicking on their name atop on of their posts, and board members can email you the same way. This is so your email address isn't hanging out there for spambots to harvest and add to their mailing lists.)
Looks like you just posted a question. Also, please use lower case font for your posting. All capital letters is akin to shouting on websites, Alvin.
If you are wondering how to start a new thread, there is an icon in the upper right corner of the partucular forum home page of your choice which you click and then make your post.
If you are wondering how to start a new thread, there is an icon in the upper right corner of the partucular forum home page of your choice which you click and then make your post.
I use a fairly tight fitting patch on a nylon brush and 320-400 garnet grit with a bit of oil. I've also used valve grinding compound which is 180-240 grit mix in water or oil. for a 10-25 strokes to start out then the same amount of strokes with 320-400 grit, then 600 grit. Once the barrel starts feeling an even drag I go to 800 grit to polish more than anything.
I have no use whatsoever for small amounts of faster burning powders except to fireform wildcat cases with one of the cereals like grits, polenta, cornmeal, cream of wheat...etc and usually use 700x or 800x, red, blue or green dot shotgun powders to keep the bulk up.
Check out Trailboss powder as it is a very bulky powder leaving little air space depending on the case size, producing low velocities and it works great with lead or jacketed bullets impregnated with a medium grit.
Or you can just to it the old fashioned way...buy some heavy, long cast lead bullets, use a medium velocity load and go shooting...the barrel will wear in fairly quickly and you get the fun of shooting...WITHOUT the mess of cleaning out the grit.
Hahahahahahah
I have no use whatsoever for small amounts of faster burning powders except to fireform wildcat cases with one of the cereals like grits, polenta, cornmeal, cream of wheat...etc and usually use 700x or 800x, red, blue or green dot shotgun powders to keep the bulk up.
Check out Trailboss powder as it is a very bulky powder leaving little air space depending on the case size, producing low velocities and it works great with lead or jacketed bullets impregnated with a medium grit.
Or you can just to it the old fashioned way...buy some heavy, long cast lead bullets, use a medium velocity load and go shooting...the barrel will wear in fairly quickly and you get the fun of shooting...WITHOUT the mess of cleaning out the grit.
HahahahahahahIn 1978 I had a Ruger Blackhawk 45 Colt with a horrible barrel that put six shots into five inches at fifty yars. I used Colgate Tooth Powder to stroke that barrel with a 28 guage shotgun mop lightly dampened and rolled in the tooth powder. I'd give it twenty strokes, clean and oil it, and fire six shots at fifty yards. After the first twenty strokes it shot into less than four inches. Then after 140 strokes it shot into 1 1/4 inches for six shots at fifty yards. I have been polishing all of my New Barrels with toothpaste eversince with great results. This Blackhawk has now had more than 30,000 cast bullet rounds put through it, and it still shoots as it did then.
Been Smithing for 42 years and have used everything under the sun. Standard Colgate toothpaste is what i have used since 1978 because it is MILDLY abrasive. Two hundred strokes with toothpaste is preferable to two strokes with emory cloth. I also learned the veryhard way to avoid molybdenum disulfide and also Commercially available bullet lubes. Go slowly and clean often!
Been Smithing for 42 years and have used everything under the sun. Standard Colgate toothpaste is what i have used since 1978 because it is MILDLY abrasive. Two hundred strokes with toothpaste is preferable to two strokes with emory cloth. I also learned the veryhard way to avoid molybdenum disulfide and also Commercially available bullet lubes. Go slowly and clean often!
Joined
·
13,162 Posts
I've used moly almost exclusively for match shooting for over two decades with never an issue of any kind. The horror stories seem to trace back either to using cheap moly with iron contamination or high levels of free sulfur, or to not cleaning the barrels at normal intervals. The good lab grade moly stuff sold by NECO under the original patent doesn't cause trouble.
The Rifleman's Journal has good articles on the successful use of moly. Scroll down the index to find the Moly heading in bold type. Read the 5 articles from the bottom up.
There's an article on lapping/firelapping at LASC's site in which one fellow describes polishing bore surfaces with JB Bore compound. I haven't read it for awhile, but IIRC, he runs a patch of JB down the bore, leaving a fair amount behind, then shoots a lead bullet through behind it at low pressure to do the scrubbing for him. That eventually polishes the bore surface as you are doing with the toothpaste. He reports a similar result. It surprises me, as my assumption has always been the constriction needs to be leveled. It may be that's only true when it is severe enough or when the lead is too hard for the pressure level used to upset it back out to bore diameter after clearing the constriction. It may be that then simply preventing a rough bore from tearing lead off is good enough.
In an analogous vein, Varmint Al says he's quit shooting barrel break-ins. He now just runs a few patch with Flitz through for a total of about 50 strokes. If the barrel still fouls he repeats with something a little coarser like JB (again, it's been awhile since I read it but you may want to take a look). Personally, I'm now using 50 strokes of Iosso Bore Cleaner (another abrasive bore cleaner) followed by 50 strokes with Flitz, I then shoot 10 rounds using the Howa distributor's method of total cleaning and cooling and hydrocarbon removal between each shot, but no more than that first 10 shots. So far so good. Is it all necessary? Not sure. Can't afford the control barrel for comparison. It would sure be great if a gun maker would sponsor about fifty identical rifles, half to be so treated and the other half not, then check the average accuracy of each group and how many rounds you can put through each group on average before accuracy deteriorates.
The Rifleman's Journal has good articles on the successful use of moly. Scroll down the index to find the Moly heading in bold type. Read the 5 articles from the bottom up.
There's an article on lapping/firelapping at LASC's site in which one fellow describes polishing bore surfaces with JB Bore compound. I haven't read it for awhile, but IIRC, he runs a patch of JB down the bore, leaving a fair amount behind, then shoots a lead bullet through behind it at low pressure to do the scrubbing for him. That eventually polishes the bore surface as you are doing with the toothpaste. He reports a similar result. It surprises me, as my assumption has always been the constriction needs to be leveled. It may be that's only true when it is severe enough or when the lead is too hard for the pressure level used to upset it back out to bore diameter after clearing the constriction. It may be that then simply preventing a rough bore from tearing lead off is good enough.
In an analogous vein, Varmint Al says he's quit shooting barrel break-ins. He now just runs a few patch with Flitz through for a total of about 50 strokes. If the barrel still fouls he repeats with something a little coarser like JB (again, it's been awhile since I read it but you may want to take a look). Personally, I'm now using 50 strokes of Iosso Bore Cleaner (another abrasive bore cleaner) followed by 50 strokes with Flitz, I then shoot 10 rounds using the Howa distributor's method of total cleaning and cooling and hydrocarbon removal between each shot, but no more than that first 10 shots. So far so good. Is it all necessary? Not sure. Can't afford the control barrel for comparison. It would sure be great if a gun maker would sponsor about fifty identical rifles, half to be so treated and the other half not, then check the average accuracy of each group and how many rounds you can put through each group on average before accuracy deteriorates.
Joined
·
357 Posts
Entry lands wear from fire lapping
Does a bullet get better alignment by forcing into symmetrical sharp cut lands rather than entering a barrel where the lands ramp up?
I have now fire lapped two stainless Ruger SBH 44mag barrels. Both times I used Beartooth Bullets firelapping bullets and compound supplied by Beartooth.
The first time I way overdid it because I could still feel a constriction at the muzzle. I should have left the constriction. I should have test fired for accuracy along the way, but instead kept fire lapping (more than 100 shots). One result was the lands at the beginning of the rifling were mostly erased and gradually rose up over a length of about 3/4 inch. The wear on each land was visibly different than the wear on the others -- there was different taper and height as each land ramped up to the point where all appeared to be identical the rest of the way to the muzzle.
I wondered if that was making the hard lead BTB bullets or copper clad XTPs have the center axis somewhat out of alignment by the time they arrived at the full height lands for the rest of the trip down the barrel?? The final result was the gun shot pretty accurately, but I think it could have done better if I had not overdone it.
If the ramping is not as good as square cut, perhaps hand lapping should be preferred over fire lapping.
Two years ago a reputable gunsmith replaced the original 4-5/8 inch SBH barrel with a new 7-1/2 Ruger barrel to hopefully get better open sight accuracy. I wanted the benefit of lapping and stayed with fire lapping instead of hand lapping because of the simplicity of it. This time I asked a lot of questions on the BTB forum and, not wanting to overdo it, firelapped it with only 30 shots. I would shoot 6, clean thoroughly, then shoot another 6, etc. I was surprised that once again I got the erosion on the beginning of the lands -- they are definitely ramped. Not as much as on the first barrel, but still very visibly ramped. Would the barrel be better if the lands were squared up with a sharp cutting leading edge rather than the squeezing action that I imagine takes place as the bullet forms into the lands and grooves?
BTW, in regard to the discussion about using fillers where there is a lot of air space in the case: For firelapping I used about 3.2 grains of Hodgdon Titegroup that I chronographed about 350-400 fps. I chose Titegroup because of Hodgdon's apparently true statement that Titegroup is case insensitive -- it doesn't matter where the powder is gathered or scattered in the case -- and my own testing verified that. I would shoot some after tipping the barrel up, some after tipping the barrel down, and some after shaking the gun back and forth while holding it level. Chrony results were about the same for all 3 situations.
Does a bullet get better alignment by forcing into symmetrical sharp cut lands rather than entering a barrel where the lands ramp up?
I have now fire lapped two stainless Ruger SBH 44mag barrels. Both times I used Beartooth Bullets firelapping bullets and compound supplied by Beartooth.
The first time I way overdid it because I could still feel a constriction at the muzzle. I should have left the constriction. I should have test fired for accuracy along the way, but instead kept fire lapping (more than 100 shots). One result was the lands at the beginning of the rifling were mostly erased and gradually rose up over a length of about 3/4 inch. The wear on each land was visibly different than the wear on the others -- there was different taper and height as each land ramped up to the point where all appeared to be identical the rest of the way to the muzzle.
I wondered if that was making the hard lead BTB bullets or copper clad XTPs have the center axis somewhat out of alignment by the time they arrived at the full height lands for the rest of the trip down the barrel?? The final result was the gun shot pretty accurately, but I think it could have done better if I had not overdone it.
If the ramping is not as good as square cut, perhaps hand lapping should be preferred over fire lapping.
Two years ago a reputable gunsmith replaced the original 4-5/8 inch SBH barrel with a new 7-1/2 Ruger barrel to hopefully get better open sight accuracy. I wanted the benefit of lapping and stayed with fire lapping instead of hand lapping because of the simplicity of it. This time I asked a lot of questions on the BTB forum and, not wanting to overdo it, firelapped it with only 30 shots. I would shoot 6, clean thoroughly, then shoot another 6, etc. I was surprised that once again I got the erosion on the beginning of the lands -- they are definitely ramped. Not as much as on the first barrel, but still very visibly ramped. Would the barrel be better if the lands were squared up with a sharp cutting leading edge rather than the squeezing action that I imagine takes place as the bullet forms into the lands and grooves?
BTW, in regard to the discussion about using fillers where there is a lot of air space in the case: For firelapping I used about 3.2 grains of Hodgdon Titegroup that I chronographed about 350-400 fps. I chose Titegroup because of Hodgdon's apparently true statement that Titegroup is case insensitive -- it doesn't matter where the powder is gathered or scattered in the case -- and my own testing verified that. I would shoot some after tipping the barrel up, some after tipping the barrel down, and some after shaking the gun back and forth while holding it level. Chrony results were about the same for all 3 situations.
1 - 20 of 49 Posts
Join the discussion
Join now to ask and comment!