Firelapping project results

[The Blade]

Months ago, I decided to fire lap my Marlin 336 microgroove 30-30.  The decision to fire lap the gun was based on the following:

1.  The gun would only produce 1" groups at 50 yards with jacketed ammo;
2.  I wanted to convert the gun to cast bullet use only;
3.  The bore had a significant amount of corrosion about midway down its length, and more at the muzzle;
4.  The bore was rough as a cob from the chatter marks in the barrel (they were clearly visible.)

Upon loading my first cast ammo for the gun (pre fire-lap), using Lyman's 311041, I seated the bullets to the crimp groove.   The bullets, when cycled through the action, showed marks from the lands.  These first pre-fire lap bullets shot into about 2" at 50 yards.

Following 45 firelap loads, which is the number of loads that it took to observe a small amount of smoothing to the chatter marks near the muzzle of the gun, the gun will shoot 5-round groups at 100 yards in under an inch all day long.  There is now no leading, and when I clean the gun, all I get is a small amount of lube and some powder fouling.  The gun is now very easy to clean, and only requires a couple of passes with a bore snake to do the job.

The main difference in the gun now is in the rifling near the throat.  Before fire lapping, bullets seated to the crimp groove would be engraved by the rifling.  After fire lapping, I have to seat the bullets out as long as I can so that they will still function in the action, and they do not touch the rifling.  However, the results are stellar with sub MOA groups.

During the fire lapping project, I used soft oversized cast bullets rolled in Clover 320 grit silicone carbide abrasive in a grease mix.  The bullets were lit off by 3 grains of bullseye in 6 round groups, cleaning and inspecting between groups.  I DO NOT RECOMMEND THIS PRACTICE FOR ANYONE WHO DOES NOT WANT TO ERODE THE RIFLING NEAR THE THROAT OF THEIR GUN.  I was willing to risk the gun, 'cause, otherwise, it was a clunker.  Now I wouldn't sell it for $500.

That's my story.

The Blade

[Nobade]

Thanks for the update! Your findings are pretty much consistant with mine regarding Marlin barrels. Get 'em smoothed out and straight and they will shoot incredibly well. I sure wish I could find some microgroove tubes that hadn't been chambered yet. Then I could lap them first, then chamber properly. Talk about cheating in the Cowboy matches! I'm glad you found happiness with that rifle, It's fun when our tinkering pays off!

[HWooldridge]

Questions regarding erosion of the rifling origin:

1. Did you shoot for accuracy at any time during the 45 shot session or did you base the time to quit on the appearance of the tool marks?  My point is that you may have drastically increased accuracy early in the session.
2. Have you tried finer compounds to determine if they polish without removing as much barrel metal?

My dad did something similar back in the 1960's with an old 92 Winchester in 44-40 that had some barrel corrosion and would not shoot.  He used round lead balls with a small charge of Bullseye and just pushed them into a fired case by hand, then put the lapping compound on top of the ball, loaded and fired.  Don't recall how many shots but that old rifle got a whole lot more accurate after the treatment.

[The Blade]

HWooldridge,

Good questions.  I was hoping that this post would generate some interest.  It's very probable that the accuracy was achieved earlier in the session, however, I wanted to continue the process until the entire bore was affected by the work.

The muzzle had some light corrosion on one side of it, and I wanted to keep going until both the severe chatter marks and the corrosion at the muzzle were lightly lapped.

I did check the accuracy after 20 rounds, and it was dramatically improved over the initial state.  Before starting the work, the gun would shoot cast bullets in about 2" at 50 yards.  After the first 20 firelapping rounds, the accuracy had been enhanced to 1" at 50 yards.  I could have stopped at that point, and would have certainly eroded the throat less if I had.

After the 20 round point, I still had leading in the barrel, and that's one aspect that kept me going.  This was a false read, though, as I had used some metal that was provided by a friend.  I thought that the ingots were WW, however, they were pure lead.  After waterdropping the pure lead, they felt hard, similar to WW metal.  Hence the severe leading that I experienced after 20 rounds.

I have looked at alot of 336's over the past few months, and never have I seen one with chatter marks as severe as the ones in my gun (pre-firelapping.)  The chatter marks still exist, but they have been smoothed a bit.

I also had corrosion in the first 1/3 of the barrel length.  The pits from the corrosion still exist, however, the edges of the pits must have been smoothed dramatically by the fire lapping.  I'll not worry about the pitting now, considering the groups that I'm getting from this gun.  I fired 60 rounds through it last weekend, and there was absolutely no leading in the barrel.  As a matter of fact, my last 5 shot 100-yard group of the day was one of the best, and it measures just a hair under 0.60".

I haven't decided if I will fire lap any of my other guns.  I have a stainless M700 in .280 that fouls badly (copper fouling).  However, until the barrel is fouled (which usually takes 10 shots or so), the gun groups very nicely.  I don't want to erode the throat, so I probably won't do it.

As to your second question, no, I've never tried any finer grit compounds.  That might be the way to go on the .280.

I've seen another trick using lapping compound to treat the crown of a gun.  A buddy of mine tried this one.  He took a glass marble, coated it with the same Clover lapping compound, and rolled the marble on the crown of his barrel until the crown was fully shined.  His accuracy on his .22 doubled as the result of his work.  It didn't even take him half an hour to accomplish the "recrowning."

Are you thinking of fire lapping a firearm?

The Blade

[HWooldridge]

Blade,

I like to shoot cast bullets and think this would benefit any firearm with a rough bore.  I know that modern weapons manufacturers spend little time in refining the bore and I think it would be a measurable benefit to try this technique more often.  I have an older 45-70 Sharps replica with a mirror bore but it will not shoot paper patch because the rifling origin is sharp and tears the patch so I am thinking about trying fire lapping to soften the transition.

The crowning trick with the marble also works with a brass, round-headed screw rolled in lapping compound and rotated against the barrel with a drill (carefully) or in a lathe.  The only issue is that the larger calibers require a screw with a LARGE head...H

[The Blade]

Last year, I ran about 20 firelapping bullets through my 1895 GG (45/70), and it'll shoot with the best of them.  I have not yet taken the gun out for serious accuracy testing yet, but at 50 yards it will print three shot cloverleafs with an aperture sight.

I'm not sure if firelapping will round off the edges of your lands, but I'm betting that it will.  Just go slowly, and test often.  Be mindful of your throat...Maybe someone who has more experience (or a bore scope!) could let you know what they've found with paper patch bullets.

Let me know how you fare with that gun.

The Blade

[HWooldridge]

I have an early 1895 Marlin 45-70 but sitting here in the office, I can't remember if it has MicroGroove rifling or not - I don't think it does because I recall Marlin bought the first lot of barrels from another manufacturer.  At any rate, it shoots well with both cast and jacketed (2 in or less at 100 yds) but that is with a gas check and won't perform with plain base bullets.  I may try 10 or so of the compounded bullets to see if it helps a bit.  Will let you know how it goes with it and the Sharps.

Your technique might also help the folks that buy cap and ball replicas and other blackpowder arms since the Italian makers probably don't spend a lot of time on final finish.

[The Blade]

Funny you should mention the Italian replicas.  I have a Navy Arms 45 Colt, and the bore has obvious marks on 0.5" centers perpindicular to the length of the barrel.  The thing shoots like a dream!  I traded a Ruger for it.

The Ruger ALWAYS leaded the bore, no matter what size bullet I used.  The Navy Arms gun is clean as a whistle after I shoot it.  Only problem is, it's point of impact at 25 yards is 8" left...the Ruger shot to the sights.

Can't win 'em all, I guess.  I sure do like those Italian replicas, though.

I have an original Winchester 1873 in 38-40, and you can't hardly see the rifling in the bore.  I'm sure the thing was shot many times with corrosive ammo.  Wonder what a few fire lapping rounds would do to that bore?

I remember when my dad first received the gun (it's been in the family for generations.)  He bought some factory (JACKETED!) ammo, set the gun up in a vice, attached a string to the trigger, backed off 25 yards, and lit the fuse.  Dang thing held together....it shot about an 8" pattern at 20 yards, though.

Whilst I was off in school, he took it and had it reblued.  It should last several more generations, but all the value is now gone.  He should have consulted with his #1 son first!

Let me know how that paper patching project goes.  I'm vaguely familiar with paper patching, but I'm very interested in your results!

The Blade

[HWooldridge]

It's downright peculiar which guns do and don't shoot cast or jacketed.  Several years ago, I had an original 1894 Marlin in 32-20 that was so shot out, the chamber split cases every time it was fired.  It would not keep any lead bullet on paper at 25 yds but was a real squirrel gun with factory loaded, jacketed bullets.  The bore was quite rough and had deep grooves so a firelap job may have helped.  Conversely, I have a Ruger old style Blackhawk in 45 Colt that cuts clovers with a 200 gr lead SWC (designed for the 45 ACP).  This pistol hates jacketed bullets but you can shoot the heads off quail with 8.0gr of WW231 under the 200gr bullet.  It is a mild load but very accurate.  This gun has killed a lot of game, probably because I am confident in its abilities.

I don't know if you want to chance it, but I have adjusted Colt SAA's that shot to one side by clamping the barrel in a vise (with protection) and taking a brass punch and 1 lb hammer to whack the sight a bit to correct point of aim.  You can usually move them a little before they will break and if you do, they can be silver soldered back into place.  If you are real ambitious, you can unscrew the barrel and adjust the shoulder on the barrel to allow it to screw-in just so far against the frame.  Remove metal lightly with a fine file to allow more rotation and peen lightly with a polished hammer on the finished edge of the barrel shoulder to prevent it from screwing in as far.  Hope this makes sense.

I'll let you know how I make out with the paper patch and firelap test.

[Leftoverdj]

It's an old gunsmith's trick to use a roundhead brass machine screw coated with valve grinding compound in a drill to recrown. Works good.

Were I to try firelapping, I'd sure use something finer than 320 grit to do it. I've lapped a few by hand power and I used Clover 800 grit.

There's been some mention of using Motor Mica as a dusting powder to keep Liquid Alox lubed bullets from being tacky. It's a very mild abrasive and I am planning to try that on a couple of old milsurp rifles.

[The Blade]

Motor mica?  Is this similar to the finely ground mica that Midway sells?  I've been using Midway's mica to dust bullets, and it seems very soft and non-abrasive to me.

Natural mica, which is in abundance 'round these parts, is very pliable.  I would have never thought of it as abrasive.

I've heard of old, dark milsurp bores being given new life by firelapping.  Those type of guns should be a perfect candidate for experimenting on.

The Blade

[Leftoverdj]

Motor mica?  Is this similar to the finely ground mica that Midway sells?  I've been using Midway's mica to dust bullets, and it seems very soft and non-abrasive to me.


The Blade

Same stuff, different label.

And, yup, it's a mild abrasive, as are talc and graphite. Learned that from an old mechanic whose first job had been polishing measurement standards. To him, half of a ten thousandths was a significant amount.

For our purposes, it's more of a polishing compound.

[Leftoverdj]

I don't know if you want to chance it, but I have adjusted Colt SAA's that shot to one side by clamping the barrel in a vise (with protection) and taking a brass punch and 1 lb hammer to whack the sight a bit to correct point of aim.  You can usually move them a little before they will break and if you do, they can be silver soldered back into place.  If you are real ambitious, you can unscrew the barrel and adjust the shoulder on the barrel to allow it to screw-in just so far against the frame.  Remove metal lightly with a fine file to allow more rotation and peen lightly with a polished hammer on the finished edge of the barrel shoulder to prevent it from screwing in as far.  Hope this makes sense.
.

S&W makes fixed sight guns guns shoot to where the sights say they should by bending the frame a mite. I dunno that I would try this at home. Fellow who told me about this had just gotten back from S&W armorers school and he had been as amazed as I was.

[HWooldridge]

OK - I tried fire-lapping a brand new Uberti replica 1860 Army last nite.  I purchased it new from Dixie and did not shoot it prior to the test but the bore showed some light chatter marks near the muzzle, which could be felt by lightly running the point of a needle across them.  I loaded 20 gr of 2F, a wonder wad and a .457 ball in each chamber then used grease based 400 grit Clover compound on top of the next ball up.  I didn't grease all at once because I didn't want recoil to sling off the compound.  I fired 18 shots this way, then tore down the pistol for a cleaning in hot water.  I reassembled and fired 12 as above but with no grease.  Groups ran about 2-3 inches at 25 yds with no flyers and several cloverleafs.  The only problem with these replicas is that they shoot about 6 inches high but windage is right on.  After the second session, I tore down for cleaning and inspected the barrel again.  The finish was mirror bright and althought the chatter marks are visible, they can't be felt with the needle trick.

[The Blade]

Sounds like your project was successful.  I believe firelapping is best suited to revolvers, as there is no throat to erode.  If the cylinder throats enlarge a bit, that's ok because you can just shoot larger diameter bullets.  Also, the total amount of shots through any cylinder throat is 1/6 the total amount of shots.

Before you put the lapping compound away, fire a couple of final lapping shots and clean the bore.  Then take an old bore brush, wrap several turns of old t-shirt around it, and thoroughly blacken it with lapping compound.  Making sure it's a tight fit, take the lapping bob, attached to your cleaning rod, and polish the bore with 100-200 strokes.  The barrel should actually heat up from the friction.  After cleaning, it will be mirror-bright.

Now you have new, raw, exposed metal in the barrel.  On your next trip to the range, break in the barrel just like you would a new rifle barrel.  Try cleaning in between each of the first five shots, then fire three 3 shot groups, cleaning between each group, then three 5-shot groups, cleaning again between each group.  That's a total of 29 bullets needed for the break in process.

A properly lapped, polished, and broken-in barrel is a wonderful thing.

Good luck...

The Blade

[Bug]

Do you guys think it would be practical to apply the lapping compound to the bore, instead of the bullet? It would seem, that if you applied the lapping compound sparingly to a brush, and then applied it to the bore, it would eliminate the throat erosion problem. It might take twice as many shots to lap the bore, due to the bullet somewhat pushing the abrasive ahead of it, but, using low-velocity cast loads, it seems as if it might work. Keep in mind, I'm talking about using the lapping compound sparingly, not gobbing it in there enough to cause ringing.  What'chall think?>>>>>>>>>Bug.

[444marlin]

marshal stanton over at www.beartoothbullets.com recomends fire lapping especially for guns that are going to shoot cast bullets, his technical manual is a great resource for info on how to do this. he also sells all the components for fire lapping a gun or rifle. I am going to fire lapp my 444P later this summer when things slow down a little. I might even try a .357 BH that leads badly with anything but oregon trail cast bullets.

[snuffy]

I bought a Wheeler Engineering bore lapping kit from midway. The reason was a 7mm mag Savage the my nephew bought from a pawn shop, some idiot had spun a cleaning rod in the bore with some sort of drill motor. There were scratches running ACROSS the rifling. It shot factory ammo into a 5 inch pattern at 100 yds.

Following the directions I embedded 20 for each grit,(220, 320 and 600), loaded and shot them cleaning between each grit. After that range session, I did a load work-up with 154 SST's to end up with one load at 1". The bore is noticably brighter, the scratches are less evident.

I find this kit to be a good buy. There's two ground hardened steel plates supplied to use for embedding the grit onto a bullet.

The last time I heard of clover compound was when we used it to sharpen the old reel push mower.

Oh by the way, graybeard, nice website, glad I found it. Howdy folks!