How do I know if my ML barrel needs lapping ?
08-29-2005, 01:41 PM
#1
Thread Starter
Join Date: Aug 2005
Location:
Posts: 135
How do I know if my ML barrel needs lapping ?
I read an interesting article on another ML site that described how to lap a ML barrel using automotive valve lapping compound (fine grit), bore solvent, a Teflon based lube, and some elbow grease. I trust some of you are familiar with the process so I won’t go into great lengths describing it. Anyway, how do you know if you ML barrel needs lapping in the first place or do you just lap a new barrel as a common practice? Are there any risks to lapping that I should know about? Does barrel lapping always provide benefits? If it would make it easier, I could cut ‘n paste the exact procedure here for your critique (or education). Just ask…
Thanks, -Hunter John
Thanks, -Hunter John
08-29-2005, 02:30 PM
#2
Dominant Buck
Join Date: Feb 2003
Location: Wisconsin
Posts: 21,193
RE: How do I know if my ML barrel needs lapping ?
I have lapped a number of barrels using the method you describe only I put the valve grinding compound now, on a small piece of Scotch Brite Scouring Pad. What you need to remember is lapping is a process that actually removes metal from the bore of you barrel. Therefore lapping is kind of a last resort for a rifle when nothing else seems to work to make the rifle accurate. Lapping is also used when a rifle is in such poor condition that it is about the only way to possibly save the barrel.
What you do to determine if your rifle even is close to needing any real work, is take some cotton balls and put them on a patch worm. Then slowly push that to the breech and pull it back out. If you drop a light down the bore, this in the case of a traditional rifle or in an inline shine a light through the breech towards the muzzle, look to see if any of the cotton strands are hanging from the walls of the bore.
A few strands of cotton fiber is no big deal. All bores will normally grab some of the fibers. If you see a spot that has a considerable concentration of fibers, that is usually a sign of a ruff spot in the bore. Another way to check the bore is to shoot patched roundballs through it. Then check the patches. If the patches are shredded, that is a sign of possible ruff spots in the bore of the rifle. This still does not mean that the rifle needs to be lapped. It just means it needs some attention.
Many people with new rifles will shoot a box of patched round ball through the rifle or a box of pure lead conical through the rifle. This many times will smooth out any ruff spots that were left from the milling of the barrel. It will also many times improve the accuracy of the rifle too.
Another easy way to smooth a barrel is with some J-B Bore Paste and some Scotch Brite Pad. Take a patch worm and put a small amount of pad on the worm. Now dip that in the bore paste and give the barrel 50 strokes. A stroke is down and all the way back up. Change or re-dip the pad every 15-20 strokes. After that wash the barrel with hot soapy water and then run some solvent patches through it. It should shine like a new silver dollar now.
Many years ago a person shot their sidelock rifle during hunting season and then for some reason unknown to me, they just propped it in a corner in the basement unattended for the next five months. When they finally saw it there the rifle was a mess. Rust was all over the outside of the rifle, the nipple was rusted into the rifle, and the bore of the rifle was all rust. They considered it a lost cause. So they gave that rifle to me, thinking I could use parts off it. Instead, I took valve grinding compound and lapped all the rust out of the barrel. Then I took J-B Bore Paste and polished the barrel. Then at night when having nothing to do I continued to run hot soap and water patches through the barrel. Finally, the patches came out light gray. I cleaned the outside of the barrel, put a new hot shot nipple on it, and now, it shoots perfect bulls all day long with 70 grains of Goex 3f and a patched roundball. That's a case where the barrel had to be lapped.
Another rifle was brought to me and we tried everything to make that rifle shoot. It would not hold a constant group. I finally lapped the barrel doing only a 30 stroke lapp. After I polished the bore and cleaned it, the rifle suddenly began to behave and they are still shooting and hunting with that rifle as far as I know.
Most new rifles if you lapp them, make it a very light lapp if any. I actually prefer to see someone if they feel it needs work to J-B Bore polish the bore. Do about 50 strokes and then clean it. It will often times make a stubborn rifle behave...
What you do to determine if your rifle even is close to needing any real work, is take some cotton balls and put them on a patch worm. Then slowly push that to the breech and pull it back out. If you drop a light down the bore, this in the case of a traditional rifle or in an inline shine a light through the breech towards the muzzle, look to see if any of the cotton strands are hanging from the walls of the bore.
A few strands of cotton fiber is no big deal. All bores will normally grab some of the fibers. If you see a spot that has a considerable concentration of fibers, that is usually a sign of a ruff spot in the bore. Another way to check the bore is to shoot patched roundballs through it. Then check the patches. If the patches are shredded, that is a sign of possible ruff spots in the bore of the rifle. This still does not mean that the rifle needs to be lapped. It just means it needs some attention.
Many people with new rifles will shoot a box of patched round ball through the rifle or a box of pure lead conical through the rifle. This many times will smooth out any ruff spots that were left from the milling of the barrel. It will also many times improve the accuracy of the rifle too.
Another easy way to smooth a barrel is with some J-B Bore Paste and some Scotch Brite Pad. Take a patch worm and put a small amount of pad on the worm. Now dip that in the bore paste and give the barrel 50 strokes. A stroke is down and all the way back up. Change or re-dip the pad every 15-20 strokes. After that wash the barrel with hot soapy water and then run some solvent patches through it. It should shine like a new silver dollar now.
Many years ago a person shot their sidelock rifle during hunting season and then for some reason unknown to me, they just propped it in a corner in the basement unattended for the next five months. When they finally saw it there the rifle was a mess. Rust was all over the outside of the rifle, the nipple was rusted into the rifle, and the bore of the rifle was all rust. They considered it a lost cause. So they gave that rifle to me, thinking I could use parts off it. Instead, I took valve grinding compound and lapped all the rust out of the barrel. Then I took J-B Bore Paste and polished the barrel. Then at night when having nothing to do I continued to run hot soap and water patches through the barrel. Finally, the patches came out light gray. I cleaned the outside of the barrel, put a new hot shot nipple on it, and now, it shoots perfect bulls all day long with 70 grains of Goex 3f and a patched roundball. That's a case where the barrel had to be lapped.
Another rifle was brought to me and we tried everything to make that rifle shoot. It would not hold a constant group. I finally lapped the barrel doing only a 30 stroke lapp. After I polished the bore and cleaned it, the rifle suddenly began to behave and they are still shooting and hunting with that rifle as far as I know.
Most new rifles if you lapp them, make it a very light lapp if any. I actually prefer to see someone if they feel it needs work to J-B Bore polish the bore. Do about 50 strokes and then clean it. It will often times make a stubborn rifle behave...
08-29-2005, 02:33 PM
#3
Fork Horn
Join Date: Feb 2003
Location: Edson, Canada
Posts: 216
RE: How do I know if my ML barrel needs lapping ?
What lapping does is remove material from the barrel normally by using a gritty compound. Some people say to do this on a new rifle and some say to use this on a rifle that is pitted or otherwise marred.
Remember that when you lap a barrel you are removing material and thereby increasing the size of the bore. I would be VERY cautious about using it and on a new rifle I would just fire it to break a new rifle in.
Eric
Remember that when you lap a barrel you are removing material and thereby increasing the size of the bore. I would be VERY cautious about using it and on a new rifle I would just fire it to break a new rifle in.
Eric
08-29-2005, 05:06 PM
#4
Typical Buck
Join Date: Mar 2005
Location:
Posts: 878
RE: How do I know if my ML barrel needs lapping ?
I have seen bores that look like sewerpipes shoot bulls all day and bores that look like mirrors hit nothing. Luck of the draw I have a friend who collects old military bolt rifles so I have seen and shot the good the bad and ugly.
FYI he has never lapped one of those bores. (over 100 rifles)
I would just keep shooting the rifle first, it will break it in harden the steel and you should be "ok". Try a bunch of loads to make sure it is not just the load causing problems. I would not ever lap a new gun. Then again I have never lapped any gun
FYI he has never lapped one of those bores. (over 100 rifles)
I would just keep shooting the rifle first, it will break it in harden the steel and you should be "ok". Try a bunch of loads to make sure it is not just the load causing problems. I would not ever lap a new gun. Then again I have never lapped any gun
08-30-2005, 06:03 AM
#5
Join Date: Dec 2003
Location: S Texas
Posts: 1,037
RE: How do I know if my ML barrel needs lapping ?
I'm a firm believer in lapping every barrel on every rifle I build. After lapping the first one, the difference was almost unbelievable. Loads much easier, cleans up easier. I lap breech to muzzle, so the barrel is "choked" slightly, about .002 from brech to muzzle. I used the directions from Robert's The Muzzleloading Caplock Rifle.
08-30-2005, 10:22 AM
#6
Nontypical Buck
Join Date: Aug 2005
Location: New Mexico
Posts: 1,081
RE: How do I know if my ML barrel needs lapping ?
You have a lot of good information above.
I have only lapped 1 gun so far, a 50cal Bobcat. It was tearing the patches and just would not group well even after trying several loads. I used the a combination of fire lapping and hand lapping. MidwayUSA.com has the kit I used (not sure what the grit #'s are, just course, medium and fine).
A few things to keep in mind are:
Slug the bore before you start to verify the bore dimentions.
Slug the bore after each step to see where you are. I didn't do this and almost blew it.
Don't try to rush it, you can mess it up quick if you do. Removing material is easy, putting it back is expensive.
The Bobcat came from the factory with a tight bore of about .498. I shot about 8 or 10 rounds with the course compound, about the same with the medium compound, and around 5 rounds with the fine compound. At that point the bore was almost to .500. I had been told this should only take out about .0005 to .001 so I was suprised that it had removed almost .002. I finished the job with 50 or so hand strokes with the fine compound and another 50 or so with some extrafine(1200) compound I got from a machinist. The final step was around 50 strokes with J-B bore paste.
The final results: bore is right at .500 and the gun can put all it shots into a 1" ragged hole at 25 yards (if I do my part). Before it would barely group 3" at 25 yards.
Again, remember to take it slow and good luck it you need to go this route.
I have only lapped 1 gun so far, a 50cal Bobcat. It was tearing the patches and just would not group well even after trying several loads. I used the a combination of fire lapping and hand lapping. MidwayUSA.com has the kit I used (not sure what the grit #'s are, just course, medium and fine).
A few things to keep in mind are:
Slug the bore before you start to verify the bore dimentions.
Slug the bore after each step to see where you are. I didn't do this and almost blew it.
Don't try to rush it, you can mess it up quick if you do. Removing material is easy, putting it back is expensive.
The Bobcat came from the factory with a tight bore of about .498. I shot about 8 or 10 rounds with the course compound, about the same with the medium compound, and around 5 rounds with the fine compound. At that point the bore was almost to .500. I had been told this should only take out about .0005 to .001 so I was suprised that it had removed almost .002. I finished the job with 50 or so hand strokes with the fine compound and another 50 or so with some extrafine(1200) compound I got from a machinist. The final step was around 50 strokes with J-B bore paste.
The final results: bore is right at .500 and the gun can put all it shots into a 1" ragged hole at 25 yards (if I do my part). Before it would barely group 3" at 25 yards.
Again, remember to take it slow and good luck it you need to go this route.
08-30-2005, 10:39 AM
#7
Dominant Buck
Join Date: Feb 2003
Location: Wisconsin
Posts: 21,193
RE: How do I know if my ML barrel needs lapping ?
I had to give my Mountain Stalker a gental lapp too. The bore was real ruff and was tearing patches. I simply did it with the valve grinding compound and a chunk of Scotch Brite pad. It sure made a difference in the accuracy of the rifle. Like I have said before, this $39.95 rifle is a real shooter now.
