Fire lapping the reference, experiences, & thoughts

[freebullet]

I've read most of what Google has to offer. Never had a bore I felt needed or could see much benefit the from the fire lap process. So, I've brushed up some as I have a barrel I think may be helped by this process.

I wanted to start a conversation to see what everyone's take is on the matter. Please post your specific experience, links to best references, or just your felling on the matter.

 

[Ian]

I've done several rifles and a couple of revolvers and employed several different methods. In general, if truly indicated and done in a manner appropriate to address the specific issue at hand, I have found fire lapping to be highly effective and very much worthwhile. I also consider it a last resort.

 

[Intheshop]

No borescope here....it's on the list.

JB borepaste and Remington 40x is as aggressive as I ever done.

Follow the directions if getting a "kit".My gut says,if the barrel is at the point,roughness wise,....done judiciously,it can't hurt.

Have you scoped it?

 

[Brad]

I have done a few revolvers and it did help. Less is more, we can take more off but we can't put any back.
I pretty well followed the instructions in a book from Beartooth Bullets. Worked like a charm.

 

[RBHarter]

I used several articles on CB as guides for a roll stamp intrusion . It was very effective . In my case I had a .310 leade to a .300/308 into an oval of .306/308 to a muzzle of .298/305.
It's about .301/308 ,round and .300/308 .
Jacketed accuracy was unchanged , naked cast improved in the sense that it remained the same but gained 150 fps and no leading in the middle of the bbl . Paper patch however was a significant gain going from 3" of repeatable 2" wander from poh to 2" plus shooter error same loads .

 

[KHornet]

Have done a couple of rough bbls on milsurps, and it worked well.

Paul

 

[Canuck Bob]

http://beartoothbullets.com/tech_notes/archive_tech_notes.htm/19

This is a comparison of fire lapping for a 444P. The three part series is worth reading.

 

[Creeker]

I have two Ruger Blackhawks, both 45 Colt, both choked at the barrel/frame junction. I used the Beartooth Bullets Kit, followed directions measuring with pin gauges as I went till the pin gauge fell through freely. I used a 200 grain SWC bullet unsized which measures from this mould .455 from pure lead. I loaded 3 grain of Promo in unsized cases fired in these sixguns & belled the mouth slightly & seated the bullet inside the case, resting against the powder.

I would fire six rounds & wipe the cylinder & barrel with paper towel patch soaked with WD40 on a cleaning jag. Once clean I fired 6 more. I went home, cleaned the gun & tried the pin gauge. I went back & repeated the process firing a total of 24 rounds in each gun. This took the choke out & left a shiny bore. Both Blackhawks shoot fine & LEAD NOT. Hope this helps.

 

[gman]

Fire lapped Super RH #1 as it had thread choke pretty bad. Can't recall the measurement. After talking with Veral Smith I ordered his LBT lapping kit. Took 200 rounds to get the choke out of that gun. Ruger stainless is tough stuff. Push a slug down the bore and it feels like it's rolling on ball bearings. His grit may be finer than the Clover compound Beartooth sells. It made a shooter out of it. Of course it was shoot 6 clean and check.

 

[Creeker]

Ruger stainless is tough stuff.

AMEN

 

[Ian]

Insanely tough.

 

[Brad]

Beartooth suggests using a coarser grit on Ruger stainless guns for the first shots. I listened after running over 50 with 320 grit thru my stainless GP100.

 

[popper]

Educate me please. Got a Marlin 336 that has the roll stamp problem. Why run slow and soft alloy? I'd like to just smear some fine Clover on the nose of my softer GC that run about 1500 fps. Is it a crown problem or throat expansion?

 

[JWFilips]

When I fire lapped my JP Sauer mauser ( heavily corroded barrel) once I got it somewhat smooth going from 150 grit to 320 grit coated alloy bullets
I switched to a gritted greased patched run into the muzzle stopping 1" before the throat. Then fired a dry alloy bullet.This prevented excess lapping of the throat area
Did this proceedure for 25 more shots with 320 grit and 25 shots with 400 grit Cleaning the barrel between each shot.
It was tedious work but it Got the Old girl shooting again

 

[Brad]

Educate me please. Got a Marlin 336 that has the roll stamp problem. Why run slow and soft alloy? I'd like to just smear some fine Clover on the nose of my softer GC that run about 1500 fps. Is it a crown problem or throat expansion?

Slow because you don't want leading. Soft because you want a bullet that doesn't have "memory". If the bullet hits a tight spot and is reduced in diameter you want it to stay smaller. The goal is to get rid of tight spots, not just polish them. Done properly you almost get a reverse taper with the breech the largest and muzzle the tightest.
This is why jacketed aren't the best either. Spring back means the bore is merely polished but tight spots aren't removed.

 

[Ian]

Excellent explanation, Brad.

Also, you need the driving bands physically embedded with the compound, just smearing a little on the noses won't do much but wear out the throat. In a revolver you can coat the forcing cone and shoot out thread choke if you don't want to enlarge the cylinders, but in a rifle, embedded slugs is the way to go.

 

[Brad]

Yep. I use a couple of small steel plates. Put compound on bottom plate and place a couple bullets on it. Use top plate and firm pressure to roll bullets back and forth thru the compound. Goal is to embed compound into the drive bands. This isn't lube, you are making a lap. Get the grit where it will contact the bore.

 

[Pistolero]

I know many have no lathe, but there are gunsmiths, too. I cringe at fire lapping out bbl restrictions
when it is so easy to unscrew the bbl, take off .001 or .002 from the shoulder on the barrel and screw back
in hand tight, or a hair more, with blue Loctite. They always are choke free at that point, and never unscrew.

Bill

 

[Brad]

That works for thread choke but doesn't eliminate other potential tight spots in the bore. Roll marking in some cases can be felt on the inside of the bore. Fire lapping will remove those restrictions too.
Key to fire lapping is not going to far and following the procedures closely. Beartooth bullets has good, easy to follow instructions that worked well for me. I like the recommendation to use a 7/8-14 bolt as a seater to keep grit out of your dies.

 

[358156 hp]

There are a number of places that can get constricted in a barrel. Lever-actions rifles have lots of opportunities for lapping because barrels can get restricted from practically any machining operation. I've seen constrictions at sight dovetails and sight mounting points, and even the little notches for barrel bands as well as the most common frame junctures and even threaded muzzles, and rollmarks. My first impression is that the factories probably use their machine tools too long before sharpening, and/or replacing. I understand the need for thrift, but it's way overdone these days.

Rugers "Terhune Anticorro" stainless is seriously abrasion resistant, my usual Ruger revolver procedure is to first start with a batch of 18-24 coarse (220) lapping bullets, followed by the same number of medium (320), bullets, and finish up with at least two cylinders of fine (400) bullets. I clean out the bore between shots with a bore snake and inspect for leading before firing more. Then I take it home, clean really well, and reslug everything, even the throats, and reevaluate. Notice the lapping bullet count is in sets of six. The cylinder throats will lap during the process as well, but at a lower rate of one bullet for every six that go through the bores. I like to keep things as uniform as possible. One of the things I look for is the degree of polish from the forcing cone forward. It will appear smoother and highly polished for the first few inches. Don't try to make the entire bore look like this, a properly lapped bore will be larger in I.D. at the forcing cone end, and the muzzle end may not show much at all. This is the way is should be, and what you've created is a slight amount of bore taper from rear to front.

When you have your restrictions removed, make sure you clean everything well, and reslug one more time, it is possible you may need to change your bullet sizing diameter slightly, but I've never needed to do it. Since I've lapped primarily Rugers, I can't offer much experience with other stainless guns, although S&W barrels seem less abrasion resistant. Blued guns seem much less abrasion resistant, and have often come clean for me with only medium and fine grit compounds.

(sigh) way too much text for people who have already done this. My new word for the day is "didactic".