Advise for hand lapping dark pitted bore?

vagrantviking

vagrantviking

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I'm hoping a few of you have tried hand lapping neglected black powder era barrels and have advice on what gives good results or warnings for what not to do.

Based on what little I could find online, I'm thinking of pouring a lead lappe in the muzzle end about 3 inches long around a rod inserted from the action then pushing it out the end and cutting some shallow rings to hold grease and valve grinding compound though not sure what grade would be appropriate. Working it back and forth I'm a little concerned that it will take more material at the ends when changing direction but can't see how that can be avoided. Coming all the way out risks losing the orientation in the rifling.
The lappe will probably have to be recast several times and finer grades of grinding compound used I presume.
This sound like a reasonable plan?

More background information for anyone interested:
I have a pair of 1890's Marlins and I'm hoping to make them usable until there's an opportunity to re-line or rebarrel but that might take quite some time to get to.
Neither has any collector value. One is an 1889 in 32-20 but the barrel, magazine tube, and stock are incorrect replacements. It has a shootable barrel but is dark and pitted ahead of the chamber but not too bad after the halfway point. Anyone happen to know if an 1894 barrel will fit the 1889 action?
The other is an 1894 in 25-20 with mismatched replacement action parts. After removing lots of black, some red rust and a little lead with patchs and copper Choir Boy scrubbing pads it's got strong rifling but the full length is very dark and rough. It snags lint tufts from a cotton patch and looks terrible. Should have bought the liner Ardent had listed but didn't realize just how awful it is.
 
I fire lap a lot of my barrels for cast bullet shooting.
I use the LBT lapping compound which is very fine, and very expensive.
About two decades back, a friend and I fire lapped his 8 mm. sporter.
It was very accurate for the first three shots, dropped off after five, and after ten, it was a real beast to clean.
After fire lapping, it was very accurate for five shots, and he could get ten off with good accuracy.
He was happy with the improvement.

There is no visual improvement, but it does smooth out some of the pits and tool marks. Accuracy is better and cleaning easier.
On some revolvers, especially Rugers, the barrels are screwed in very tightly, to the extent that the bore diameter under the threads is measurably smaller than the rest of the bore.
Fire lapping is the only cure.

Some bench rest gurus swear by it and others recoil in horror that it will erode the leade most of all.
However, if there is lots of metal removed, it will give a tapered bore, like the Parker Hale muzzle loaders had.

As in all things, YMMV, and your own due diligence is required.
 
drill702 said:
How about just shooting it and letting the lead fill the pits?
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I'm pretty sure that was the idea of the past owner. LoL To a degree it was working too as it looked better before I started cleaning.
Two main concerns with this approach are lead building up until the rifling isn't doing anything but chewing the bullet all to hell and corrosion continuing in the pits under the lead. This is especially a problem if I end up shooting black powder which I would like to in at least the 32-20 if the action feeds well.
 
I will have to reconsider fire lapping. My thought was that it would take material from the throat and not do much for the rest of the bore or maybe be ineffective with the very fine compounds usually used. More research is in order. Thanks Slug.
Your point about creating a tapered bore makes sense so that's not necessarily all bad. If nothing else it might be a headstart on the hand work which is going to be a long onerous task at best. Shooting would be more fun than a week pulling the rod back and forth.

Next time I look at my Rugers I'll have to see if I can feel any tightness at the frame. Wasn't aware of this possible issue. Thanks for another project! LoL!
 
Cast a lap. Charge with 240 grit Clover compound. When lapping, stop about three inches from the muzzle for the first fifty strokes then alternate to the muzzle for fifty more. I set the barrel up with a stop so I can push the lap just out of the barrel without going clear out. The clover compound will break down as you work. After 100 strokes or so, cast a second lap and charge with 500 and repeat. To finish, use steel wool wrapped around a jag and charged with JB. Give about fifty strokes. The idea is to end up with a slight choke which will ease loading. As the lap loosens, it can be bumped up by sliding a rod down and bumping it against the lead lap.
 
Using Clover brand grit is important. It is non-embedding. It breaks down after about 10 strokes. The valve grinding compound never breaks down and some will stay in the bore.

I have fire lapped a muzzle loader with Clover (5 grits) and it worked well.
 
If you can't find lapping compound in appropriate grits (valve grinding compound is pretty aggressive stuff), Lee Valley has lapping grit that you can mix with grease to make your own compound. I used the 400 grit to fire lap my M&P 22 to correct a fouling/accuracy problem.
 
while I'm not going to go against lapping in general, I think in this case it would not be well advised. You stated the bore is "pitted" and I can see a lot of the lapping compound being deposited from the slug into these pitting's and staying there forever and every shot you fired subsequently will pick up a bit of the grinding compound causing more "lapping " (premature barrel wear) than you hoped for.

Personally I have found that a little pitting and a dark bore isn't a death-knell to an old barrel, usually if they have enough rifling left to spin/grip a slug they will shoot 'passable. Some of the really black ones I have pushed a well oiled wad of steel wool once or twice down the bore just to "take the thick stuff" off and them shot them.
 
While there are certainly people who have more experience in this than I, I've lapped enough barrels to be pretty familiar with the process. The process for trying to resurrect a pitted barrel is a lot different than lapping a new barrel. Also, lapping a barrel for a muzzle-loader is a different proposition as well. Lapping is often employed to achieve a desired internal finish, especially when lapping a barrel for use with jacketed bullets, and not usually intended to alter dimensions too much. When lapping a muzzle loader barrel, one often wants to alter dimensions a bit so the approach is different. I must also mention that things are different for a barrel to shoot a patched ball than to shoot an unpatched lead bullet.
 
I believe there is a big difference between lapping a machined bore that may be a bit rough and lapping a worn out, neglected and pitted bore.

All you can do with the worn out and pitted bore is remove even more material, it will not 'sharpen up' anything.
 
I don't have near the experience of the two previous posters, but my limited attempts are in agreement with them. I have a "Boer" Mauser - verified by David George to be original. Bore had very obviously been "rode hard and put away wet". My research said my challenge was to get as much grunge out of the pits and rifling grooves as possible, then just shoot with jacketed bullets. Cleaning took weeks. Overnight soak with Wipeout foaming bore cleaner. Brass brushing with copious amounts of RB17 gel. Found a section of heater hose that matched the diameter of the muzzle - rad clamped it on and filled bore with penetrating oil (50/50 ATF and Acetone) Plugged the chamber and let it soak overnight. Hosed down the bore with spray brake cleaner. Repeat all above many times and used dozens of patches along the way. Patches actually come out white now, and there are sections of "shiny" but still lots of dark. I think that is all that can be done, short of having new bore and threads cut for larger diameter bullets.
 
Ganderite said:
Using Clover brand grit is important. It is non-embedding. It breaks down after about 10 strokes. The valve grinding compound never breaks down and some will stay in the bore.

I have fire lapped a muzzle loader with Clover (5 grits) and it worked well.
Click to expand...

I'd read Clover was the stuff most popular but hadn't figured out why exactly. Thanks for filling in that part of the puzzle.
 
guntech said:
I believe there is a big difference between lapping a machined bore that may be a bit rough and lapping a worn out, neglected and pitted bore.

All you can do with the worn out and pitted bore is remove even more material, it will not 'sharpen up' anything.
Click to expand...

It certainly won't fix most of what is wrong but low velocity cast bullets are pretty forgiving. In my experience even quite washed out barrels can shoot them better than expected.
I just want to be able to fire a couple dozen rounds now and then without worrying that it will be a multi-day process to clean and scrape out the lead buildup.
 
guntech said:
I believe there is a big difference between lapping a machined bore that may be a bit rough and lapping a worn out, neglected and pitted bore.

All you can do with the worn out and pitted bore is remove even more material, it will not 'sharpen up' anything.
Click to expand...
There is indeed. A pitted muzzle loader barrel can be lapped out because dimension is not all the critical. You are right in saying nothing can be sharpened up with a lap. In the case of a severely pitted barrel, the old time 'smith could cast a lead alloy slug then inlet a cutter into the slug and freshen the barrel that way. The method was described by Horace Warner. This worked because a muzzle loader could be any caliber and it was easy enough to fit a ball and patch to it.
 
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