Fire Lapping

Gentlemen, good day. I wanted to use the knowledge of you all regarding Fire lapping. I have read several articles about it and have never gone through the process or met anyone personally who did it. It seems to be a method to remove imperfections from a barrel... in particular one that appears not be in good shape. I have been signed onto this site for only a few months and found some good information... all that said... I am just wondering you opinion of the process? if it is helpful? if it can cause more problems than cures? etc.

Thanks for any comments...

Fire Lapping for round ball in my opinion would be a waste of time, energy and money. Scotch Brite or fine steel wool would be much easier and effective for a rough bore.

I'm no expert. Less than an amateur actually, but how much good does fire lapping a muzzle loaded bore do? you are lapping both in and out so I see some double benefit. I also see an easy way to
over lapp...

The problem with a muzzleloader and ball is consistency.
With a breach loader and a grooved bullet passing just the once one can regulate it readily.
The same could be said with a minie by filling the grooves but a patch ball make possibly bare unevenly on the loading stroke and bear differently on firing.

For a ball rifle I recommend hand lapping.

All my opinion and thus unqualified and of extremely little value.

FPG52 said:

Gentlemen, good day. I wanted to use the knowledge of you all regarding Fire lapping. I have read several articles about it and have never gone through the process or met anyone personally who did it. It seems to be a method to remove imperfections from a barrel... in particular one that appears not be in good shape. I have been signed onto this site for only a few months and found some good information... all that said... I am just wondering you opinion of the process? if it is helpful? if it can cause more problems than cures? etc.

Thanks for any comments...

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I have done some fire lapping in both percussion pistol and cartridge rifles. It works well in cartridge guns as the bullet only travels in one direction. I found in one of the rifles I did this to that the chamber throat was lengthened more than was change to boar diameter. It did to quite a good job of smoothing.
Fire lapping does not do much past about the lower third of the bore. It cuts quite aggressively at first but peters out pretty fast up bore.
I fire lapped a 58 Rem and ruined the forcing cone which had to be re-cut to restore accuracy.
I have hand lapped quite a few barrels with poured lead laps and especially made lapping rods with bearing handles. This is the very best method as one has much more control over the cutting action.
Revolver barrels are best lapped while still in the frame as the thread pressure tends to choke the bore a bit in that part of the barrel.
A muzzle loading rifle barrel should have the breech plug removed and lapped from breech to muzzle.
A freshly charged lap should not be introduced into the muzzle but rather the breech as it cuts most aggressively at the very beginning.
Cartridge barrels can just as easily be lapped as muzzle loading barrels as I have done a fair number of both personally.
Far as I can tell a level boar will shoot just as well as will a bore with a bit of taper lapped in.
Some of the old time muzzle loading match barrel makers ( Warner and Brockway to name a couple) experimented extensively with gain twist and taper choking. They both settled on level bores with a bit of choke in the last few inches at the muzzle with even twist rifling.
The choke is lapped in and is only a few ten thousands.

Lube a few maxi-balls with valve-grindin’ compund or other similar abrasive.

M De Land is guiding you in right direction. I too have lapped many barrels mostly cartridge guns and a few muzzle loaders. A good muzzle loader barrel can be improved with carful lapping and a rough or neglected bore will not become a good one. I did a new Lyman barrel once that had many machine marks in the bore and after hours of work it was OK but never shot as well as a decent manufactured barrel.

Fire lapping was designed for cartridge guns not muzzle loaders. Fire lapping slugs (not balls) are cast of pure lead usually which has quite a bit shrinkage. This allows room for grit impregnation. The freshly cast slug is charged with the grit of choice. I usually start with 320 grit and the slug is rolled between glass or steel plates until of groove diameter of the bore being lapped.
It is sent up bore with just enough powder to clear the muzzle. The bore should be wiped between shots to alleviate powder fouling interference.
One should have a good bore scope and slug/pin gauges so that progress can be monitored and measured. LBT sells some nice kits for fire lapping along with instructions. The trick is to not over due the process. If executed correctly very good results can be had.
Still the very best method is the old fashion cast slug and lapping rod technique.

I knew I was going to learn something when I posted my question...didn't realize just how much!! Thank you all for your insights and suggestions... not sure how I will proceed now... BUT i sure have more knowledge. Thank you very much for sharing that knowledge...

I see several problems and a few more potential problems in some of the above responses.

First off, DO NOT FIRE LAP WITH VALVE GRINDING COMPOUND!! Read that again if you are still tempted. Otherwise you are going to ruin the barrel.

The use of 320 grit ANYTHING is another step down the road to ruination.

I'm talking about fire lapping. This topic has had hand lapping introduced along the way. I will only address fire lapping since that is the the question asked by the OP.

Fire lapping is an excellent way to improve a muzzle loading barrel. Exceptions are barrels that are polished in some way by the maker. Virtually all of the Italian and Spanish made barrels will benefit. I'm referring to barrels that are new or not damaged or neglected. Green mountain barrels will also benefit.

These barrels are cut rifled and have some very sharp edges on the lands and have some tool marks on the lands and in the grooves. A barrel that cuts patches will never reach it's accuracy potential with round balls. Pretty much all the barrels I mention above will cut patches and will do so for many many many many shots before they finally smooth out a bit.

So many new shooters are starting out with the very barrels mentioned above. And, so many of them give it up long before they ever even begin to break the barrel in!

If you want to fire lap a ML, you need to start with the right stuff. The three suppliers that I know provide the correct materials for fire lapping are Nico products, LBT mold manufacturing and the Wheeler fire lapping kit.

Follow the instructions and use pure lead Bullets, not patched balls. Powder charges on the light side are adequate. You MUST wipe the bore thoroughly between shots.

Done this way your barrel will load easier, not cut patches when the ball and patch are compatible and will hold less fouling and be easier to clean.

It's also very beneficial to smooth the crown and entry into the muzzle.

On all my MLS I used Ajax and a very tight cleaning patch. Get some luk warm water and make a paste with the ajax. Or commit works to. Smer it on the cleaning patch then swipe bore 100-200 times may need to reapply Ajax paste. Try it it works very well!

I like to lap my barrels with nothing but black powder, cotton patch, mink tallow and pure lead balls.
Why not just shoot it until it breaks in good. It's a lot more fun... and you have the added benefit of being outside and enjoying the day and the company of like minded friends..

Or he could fire twenty or thirty lap slugs and proceed to the same enjoyment while hitting what is aimed at.

Griz44Mag said:

I like to lap my barrels with nothing but black powder, cotton patch, mink tallow and pure lead balls.
Why not just shoot it until it breaks in good. It's a lot more fun... and you have the added benefit of being outside and enjoying the day and the company of like minded friends..

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Actually fire lapping and to a greater extent , cast slug lapping are methods to alter bore dimension where as patched ball shooting is just polishing the bore surfaces, removing machining whisker etc. not making any dimensional change.
The advantages of fire or cast slug lapping is that the bore diameter is uniformed, land corners and to a lessor extent the groove corners, maintain there sharp profiles along with whisker removal and one does not have to waste 100-150 shots before peak performance is achieved.

M. De Land said:

and one does not have to waste 100-150 shots before peak performance is achieved.

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I can see where that makes us strikingly different. I don't see spending time at the range shooting paper and plate wasting anything, either supplies or time! That's why I picked this hobby, to shoot more and grind less... And a good quality rifle does not miss anything just because it did not get lapped by some grinding powder. They still hit and very reliably. They do keep getting better and better, along with the owner getting better and better from the extra practice. Sad to see that anyone would consider shooting a waste.... (except for maybe my wife...)
I also know that 3 deer have been put in my freezer by rifles with less than 50 rounds down the tube, someone must have told them that a un-fire-lapped barrel could not kill at 75-110 yards....Guess they were told wrong...

Griz44Mag said:

I can see where that makes us strikingly different. I don't see spending time at the range shooting paper and plate wasting anything, either supplies or time! That's why I picked this hobby, to shoot more and grind less... And a good quality rifle does not miss anything just because it did not get lapped by some grinding powder. They still hit and very reliably. They do keep getting better and better, along with the owner getting better and better from the extra practice. Sad to see that anyone would consider shooting a waste.... (except for maybe my wife...)
I also know that 3 deer have been put in my freezer by rifles with less than 50 rounds down the tube, someone must have told them that a un-fire-lapped barrel could not kill at 75-110 yards....Guess they were told wrong...

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The last percussion muzzle loader I built, used a GM barrel. I hand lapped it with one poured slug using 400 grit only and it was superbly uniform in bore diameter, breech to muzzle. I should have used my standard 320 grit first and given it a hundred more strokes as it cut patches for about 75-100 shots before settling down. Each time the patch was cut it would register on target some where other than where the shot broke.
When the patch cutting stopped so did the errant shots.

A shot going some where other than where the sights register, when the shot breaks, is a waste of powder, primer , lead and patch , to me, especially when it could have been prevented.
Poor accuracy does does not teach anything I care to learn and is extremely boring in my opinion.
Also, killing a deer at 75-100 yards does not require a particularly accurate rifle.

M. De Land said:

The last percussion muzzle loader I built, used a GM barrel. I hand lapped it with one poured slug using 400 grit only and it was superbly uniform in bore diameter, breech to muzzle. I should have used my standard 320 grit first and given it a hundred more strokes as it cut patches for about 75-100 shots before settling down. Each time the patch was cut it would register on target some where other than where the shot broke.
When the patch cutting stopped so did the errant shots.

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Looks to me like you are shooting as many rounds while grinding away at your barrel as I shot breaking mine in, except I did not have a bunch of errant shots in the process. After the first 10 or so, patterns at 75 meters held very consistent at 3" and continuously shrank as the count went up. By a hundred shots I was way past settled down. You gained nothing. You have accomplished nothing with your dogged dedication to barrel grinding except convince me NOT to do something like that.... Thank you for your experience, now I know what NOT to do.

Fire lapping a barrel or hand lapping has nothing to do with how frequently you enjoy shooting. In fact, fire lapping is an opportunity to add an additional range visit.

Griz44Mag said:

Looks to me like you are shooting as many rounds while grinding away at your barrel as I shot breaking mine in, except I did not have a bunch of errant shots in the process. After the first 10 or so, patterns at 75 meters held very consistent at 3" and continuously shrank as the count went up. By a hundred shots I was way past settled down. You gained nothing. You have accomplished nothing with your dogged dedication to barrel grinding except convince me NOT to do something like that.... Thank you for your experience, now I know what NOT to do.

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You are speaking from a position of ignorance and dogma having apparently no personal experience at barrel lapping of either type.
It would be wise at this point to stop talking and listen and then investigate if what your hearing is true.
A barrels properly lapped bore of either method will not be harmed and usually can be improve if executed correctly ,to one extent or another.
Historically the very best match grade barrels were always lapped and even today many are to one degree or another, particularly if of a cut rifling (broached, single point or hooked ) method.
Your term of barrel grinding is completely incorrect. A lead lap does not grind a bore as does a wheel grinder finishing a barrel exterior, after being turned or milled. It does however smooth and uniform by abrasion (with out the heat component of grinding) through the use of a mirror image casting impregnated with fine abraisive, which maintains the machined bore profile while removing the on wanted machining foot print of whiskers, rotation scratches and small dimensional inconsistencies.
Lapping will not make a poor barrel shoot well but it will very often make a good barrel shoot better.

M. De Land said:

Fire lapping was designed for cartridge guns not muzzle loaders. Fire lapping slugs (not balls) are cast of pure lead usually which has quite a bit shrinkage. This allows room for grit impregnation. The freshly cast slug is charged with the grit of choice. I usually start with 320 grit and the slug is rolled between glass or steel plates until of groove diameter of the bore being lapped.
It is sent up bore with just enough powder to clear the muzzle. The bore should be wiped between shots to alleviate powder fouling interference.
One should have a good bore scope and slug/pin gauges so that progress can be monitored and measured. LBT sells some nice kits for fire lapping along with instructions. The trick is to not over due the process. If executed correctly very good results can be had.
Still the very best method is the old fashion cast slug and lapping rod technique.

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Beartooth Bullets sells a firelapping kit for muzzleloaders. There is an article by Marshall Stanton in their ‘Tech Notes’ section on the topic. Would post a link, but it appears they are having a server issue at the moment.