Home Forums Hunting & Shooting Ask The Gunwriters Hand-lapped barrels, fire-lapping etc... Just voodoo?

Does lapping the barrel really make any difference? From that other thread a couple of weeks ago on cut vs button vs hammer forged I learned a whole lot I did not know.

When it comes to barrels I gather the stress relief process is the most important factor of all? Is lapping the tool marks out just some snake oil or is there something to it?

That would depend on the quality of the tooling used to rifle the barrel, and that would be with a direct relationship to the skills of the man doing the work.
Quality in, equals quality out!

Lapping a bad barrel will likely not make it good, but lapping a good barrel will almost assuredly make it better.

Some else said that before.......maybe Shilen?

MM

It's kinda like finishing concrete. You need to know when to leave it alone, let it rest or are you just playing in the mud.

It's all good, only if the person doing the work is good.

With barrels, I wouldn't want a "Broom Finish"..

Most custom barrels are hand lapped before they are sold.In most factory barrels lapping makes little to no difference.Fire lapping can improve a barrels worn throat.Also works good on Revolvers to make the forcing cone and barrel the same size.JMHO ,Huntz

The only barrel that I have had any real luck with firelapping was a Marlin in 444. It had a couple of tight spots in the bore that were evident when you pushed a lead slug through the barrel. One tight spot was under the rear sight dovetail and another was where the dovetail for the magazine tube was cut into the barrel. The rifle would group into no better than 3 inches at 100 yards and mostly larger than that. This was an unusually inaccurate Marlin in my experience and was going to get sold if it couldn't be fixed. I ordered a kit with bullets and lapping compound and followed the included directions. The bore looked much smoother and groups that measured 1 inch to 1.5 inches became what I could expect from that rifle.

I have to admit that I have tried it on a couple of other rifles without such dramatic success, but it did work on that Marlin.

For real efficacy, fine barrels are lapped after they are bored and before they are rifled.

Subsequent lapping might add a little polish, but only address stuff at maybe the micron level.

Yes, hand lapping help, but it has to be done when the barrel is new, other wise you will do more harm then good.

I have a savage in .223 that didn't shoot the light bullets very well when it was new, so I hand lapped it and it seemed to help. I generally hand lap anything that's going to be running a sabot as well. Otherwise, I don't do it much anymore, although sometimes I do clean with JB bore paste, which is kind of similar.

I have a Remington Model Seven stainless, and when it was new I fire-lapped the barrel. Before doing that I could see imperfections in the barrel. After, they were gone. I can't say it improved the accuracy or not, but I think it did. What I can see is that the barrel stays cleaner.

Steve,

I've run Tubbs final finish through a few and I believe they all shot a bit better. Certainly smoother and more even when pushing a patch through. Cleaned easier too.

I had the same experience with a Marlin 1894 in .25-20. The only tight spot, though, was over the magazine tube dovetail. Made a big difference.

Almost all quality barrels are lapped. Some are lapped after reaming the bore as well as after rifling. They normally use 180-220 grit lapping compound. If you finish with 400-600-800 grit the barrel will copper foul.

butch,

Are you saying that the "finer" finish actually fouls more? That seems counter-intuitive to me. Please explain.

That's exactly what happens. Beyond a certain point, and even smoother finish results in more bullet contact with the bore, and hence more friction, resulting in more copper fouling. This is why some barrelmakers caution against using JB Compound very much in their lapped barrels. Eventually it creates an even smoother bore. Instead they like the bullet to be "riding" on top of the miniature striations created by a slightly coarser lapping grit.

JB usually doesn't affect unlapped barrels, however, because their surfaces aren't as smooth in the first place. But it can. My .338 Winchester has a take-off Sako barrel, which despite being pretty smooth tended to foul badly. Chemical cleaners took too long, so I started cleaning it with JB every time. That got rid of the fouling, but it started coming back even quicker. I was about to rebarrel the thing because it became caked with copper within 20 rounds, but then DBC came along and solved the problem.

I had a rebored rifle that was a fouling SOB. After 10 rounds, the accuracy was gone and I could make a penny out of the copper deposits. I firelapped it with lead bullets and 5 rounds of 220 grit, 10 rounds of 320 grit, 10 rounds of 400 grit, and 10 rounds of 600 grit. Afterwards the accracy was slightly better, but I couldn't get it to copper foul at all. Only took a couple patches for cleanup.So based on a sample of one,I wouldn't have an issue trying it again.

Great analogy.

John,

Not being well versed on DBC, this seems to counter your statement that the smoother lapped/polished bore fouls more due to more bullet contact.

If I understand correctly, DBC "fills in the low points", creating a smoother bore.

Would that not be the same as "knocking down the high points" by fine lapping/polishing?

I suppose it could be that the miniature striations are left in place with DBC while the valleys are filled up, leaving less room for fouling to collect.

Any ideas why DBC seems to work, while too much polishing doesn't?

Thanks,
David

It might have something to do with the different surface of DBC as opposed to steel. But I don't really know.

I had one Wilson barrel that gave me fits. Finally I was good and mad and I attacked it with coarse auto valve grinding goop on a tight patch. I took care to be consistent, but I full stroked that mutha like I meant it for about ten minutes.
I'd go until the goop dried, shove that out with Hoppes Nine, then go again with another patch of valve crud.
Had a stop block on the muzzle and a stop line in back to make sure I didn't trash the throat any worse.
Dressed the crown, cleaned the bore to white patches -- and the darn thing started drilling them in. Still have that barrel, on its second rifle.