Fire lapping a muzzle loader

[GregLaROCHE]

Has anyone had any experience trying to fire Lap an old muzzle loader. I was thinking some valve grinding compound and grease on a patch with a round ball. The other thought I had was to PC a round ball and before it cooled down, roll it in some dry grit. I guess there’s the method of rolling the pure lead projectile in grinding compound to embed it in the lead. Has anyone ever tried something like this? Any advice. Thanks.

[LAGS]

I make a lapping slug out of JB weld molded to the barrel.
Then with the slug mounted on a screw threaded into a cleaning rod.
I lap the bore with polishing compound like chrome cleaner or Mag Polish.
I cast the bore slugs on barrels that have the breech plugs out sometimes.
I also cast the slugs in the bore using a 8/32 or 10/32 Long screw with a couple washers that fit in the bore to stop the epoxy from running down the bore.
I coat the bore with Johnson's Paste Wax as a release agent.
I also leave a couple inches sticking out the end of the barrel.
Then you can use nuts , washers and a small piece of tubing to pull the plug out of the bore.
There are some pictures of this set up in the thread I did on the Bubba'ed Barrel Repair thread, in the muzzleloader section.
I used the lapping to polish down the screws I put in the holes that were drilled and tapped into the rifling
You can also mix an abrasive compound into the epoxy to make a molded lapping stone that matches your rifling perfectly.

[gunther]

A friend had pretty good luck fire lapping a 32 40 with JB bore paste. 6-7 inch groups shrank to 3 inches. Chrome paste is about the same grit. Valve grinding paste might be a bit coarse unless the barrel is a real stove pipe.

[Mk42gunner]

Seems like everybody wants to use valve lapping compound. That might be fine if you are trying to remove all rifling and make it a smoothbore, but even the fine is way too coarse to use in a rifled barrel, at least in my opinion.

I have lapped exactly one muzzle loader barrel, it was a fifty cal Sharon barrel on a flintlock of my uncle's. Somehow he let it rust for about eight inches about 1/3 of the way down from the muzzle.

I cast a lead lap about an inch and a half long by plugging the bore with rags and using a worn out .30 cal brush for the attachment point. I then used some Clover lapping paste that came in the bolt jeweling kit from Brownell's, 600 or 800 grit IIRC. An old barracks rod that had a swiveled handle helped a lot.

It did take a while, and a lot of trips back and forth; but the rifle is once again useable, and about as accurate as I remember as a teenager.

Robert

[LAGS]

I agree with the texture used to lap barrels.
The best I have found to use is Mother's Mag Polish.
It is very fine.
And when using a lapping slug that matches the rifling works a lot better than lapping compound on a patch or batched balls.
If the barrel is pitted really bad,
Then send it to Bobby Hoyt to be Refreshed.
The Mag Polish removes Stains in the bore and will smooth out the full length of the bore for better loading.
But don't get carried away or considerate in one spot.
I don't think that a patched ball with polishing compound will do a good job.
There isn't that much surface contact of the patch.
So it will just be wearing off the corners of your rifling.
But a Lead cast rifled slug that fits the rifling, or a cast epoxy lapping slug will follow the rifling and polish the bore more equally and not eat away the rifling.

[longbow]

I'll add my 2 cents worth here.

As for valve lapping compound, it is pretty fine and available in a variety of grits. Let's face it, lapped valves have to seal against the pressure developed in an engine so it can't be very coarse or the mating surfaces would be too rough to seal.

I believe the valve lapping compound I have is 425 grit.

Regardless, I had some issues with my 1894 Marlin .44 mag. with microgroove rifling. Even using fat boolits larger than broove diameter I was getting leading. So I was researching some since I haven't had problems with other guns. On the Marlin Owners forum I read that some Marlins have tight spots in the bore due to roll stamping so I made a lead slug, oiled it then tapped it into the bore and ran it through using a 5/16" rod and bore guide. Sure enough, tight spots!

So I made up some lead lapping slugs and drilled through so I could attach them to a rod then put one on the rod and ran it through the barrel until it moved without much effort. Then I coated it with lapping compound and ran it down to a tight spot, worked that tight spot until there wasn't noticeable resistance then moved to the mext tight spot. When I finished with tight spots I put a new lapping slug onto the rod, coated with lapping compound then ran that down the bore working back and forth from breech to muzzle with slightly more time spent towards the breech end of the bore. When I finished a clean lapping slug ran with pretty much even resistance from muzzle to breech.

This gun is an 80's vintage Marlin with microgroove rifling so not much rifling depth there. There is no visible "damage" to the rifling after lapping and it certainly wasn't removed! Now, I get better accuracy and no leading.

No, not a muzzleloader but the same principle applies. Make a proper lapping slug, attach it to a rod then work it through the bore with lapping compound on it.

Personally I think it better to hand lap rather than fire lapping but I guess it depends on what you want to accomplish. If just smoothing up the bore a bit or removing a light rusting/minor pitting then nfire lapping should work fine. If the bore is fairly rough, I'd be inclined to hand lap at least to even up the bore then maybe fire lap with something like the chrome polish or JB bore paste to finish it off.

For fire lapping my view is that a GG boolit sized to groove diameter then tapped into the bore to engrave the rifling on it then remove and fill the lube grooves with lapping compound then load and shoot would be far better than putting lapping compound on a patched ball. A Minie should work fine too, just fill the grooves with lapping compound then load.

I have lapped the 1894 Marlin, two .303 Lee Enfields and my 1881 Marlin .45-70 that had an ugly bore that doesn't look so bad after hand lapping.

It worked for me but as usual YMMV.

I hadn't thought of using an epoxy like JB Weld per LAGS post above but no reason that shouldn't work. Not sure if it is easier to make a lead lapping slug or epoxy lapping slug but it may depend on what you have handy for materials and tools. The lapping method I read about many years ago said to cast a lead lapping slug in the bore but I found that more work and trouble than turning a lapping slug on my lathe then tapping it into the bore to engrave it. Making an epoxy lapping slug in the bore is probably easier than casting a lead lapping slug.

Longbow

[LAGS]

The epoxy lapping lug works great.
I have used that method on many rifles.
I use to have lots of Mosins Nagants with the sewer pipe condition barrels.
Some barrels cleaned up easily.
Others took lots of time.
And honed the bores out a bit.
But the lapped bores still had functional rifling even though the bore got lapped to a little larger diameter like from .311 all the way to .314.
The easiest method to make the lapping slug was to lightly plug the barrel about 2" down the muzzle after putting in the release agent.
Then coat an old bore brush with epoxy.
Then insert it into the bore and let it mold to the rifling.
When hardened , it can be pounded out from the chamber end with a cleaning rod.
It takes a little more work on muzzleloading barrels if you don't want to pull the breech plug.
But I can pull the plug out the muzzle with other methods.
And using Epoxy works better since after lapping a bit , you can easily cast up another lapping slug as the slug wears or the bore gets larger from cleaning out.
One thing is to use a GOOD epoxy like JB Weld or bedding compound.
Don't use quick drying cheap 5 minute epoxy.
It stays sticky and kind of soft.

[longbow]

I should add a couple of caveats...

You do have to protect the bore from the rod as you lap so a bore guide is essential.

You have to lap a bit then pull the lapping slug out, clean thre bore and check progress. Running a slug through the clean bore will indicate if there are any tight or rough spots.

I won't argue that excessive lapping could damage rifling or make the bore much too large so proceed slowly and carefully.

For fire lapping, the same rules would apply. Shoot a few fire lapping bullets (like maybe 5) then clean and check the bore. Again, if you are just cleaning upo a light rust it shouldn't take much. However, if there is deep pitting it will take some work to smooth out the bore and you aren't likely to get rid of all the pitting.

I just may try LAGS's epoxy lapping slug myself next time I am in the mood to lap a bore!

A bit of added info...

I used to ahve a replica Remington Zouave that was a horrible gun! I don't remember the manufacturer but it was bought new in the 1970's and came out of Spain or Italy. It fouled terribly and no amount of lube seemed to help. I gave up on it and sold it to a friend. He figured the bore was rough from poor machining so he made a felt lap by punching out and stacking felt disks on a rod then coated that in valve lapping compound and ran it down the bore and worked it until he said it felt "smooth" with equal friction to push/pull it through the length of the bore. The gunh shot much better after and didn't foul so he was likely right about some tool marks in the bore. I didn't think the felt lap was a good idea but it worked for him.

Longbow

[stubshaft]

For rifles I usually just pour a lead lap and use NECO grit to polish the bore.

[45workhorse]

Pour your lead lap on a wooden dowel rod longer than your barrel. Index it so you can put it back in the same way it came out. Won't have to worry as much about your crown. Has work for me in the past!

[waksupi]

You can imbed your patches with fine grinding compound. Keep you charges down around 10 gr. It should take less than 20 rounds to slick up a barrel.

[GregLaROCHE]

You can imbed your patches with fine grinding compound. Keep you charges down around 10 gr. It should take less than 20 rounds to slick up a barrel.

That’s what I was thinking about. The barrel has been pretty rusted in the past. I don’t want to put too much time and effort into it. I don’t expect it to be a great shooter. I just want to clean it up a bit and maybe reduce the force required to load it.

[waksupi]

That’s what I was thinking about. The barrel has been pretty rusted in the past. I don’t want to put too much time and effort into it. I don’t expect it to be a great shooter. I just want to clean it up a bit and maybe reduce the force required to load it.

Some sewer pipes shoot great!