Fire Lapping a Barrel

[roninflag]

i would not want to shoot against kevin or david. i use jb's from time to time . i do not firelapp.

 

[Bart B]

Kevin, when at Sierra, did you ever use any of Jim Hull's "Martin's Mustard" bore cleaner?

It was made with some special oil and enough extra fine yellow colored dental pumice to be as thick as partially dried paint. Finest non-embedding abrasive known to man at the time and used by dental hygienists to clean teeth. It sure would remove copper jacket fouling as well as just about anything else that gets inside a rifle barrel coating the steel. Martin told me that if you used it for a few hours lapping the leade of the rifling, it would smooth out a lot of the slight roughness left by the reamer. He finished his talk with me saying that smoothing out the leade to be as smooth as the lands and grooves would last for a couple hundred rounds in a .308 Win barrel; after that, erosion from burning powders would rough it up all over again.

 

[Kevin Thomas]

No, I think we'd probably moved on to J-B by that point, and it was a regular treatment every couple hundred rounds or so. Same idea, though; pumice based abrasive that breaks down after just a few strokes. I think this stuff is perfectly fine, so long as it's used with some discretion. Some barrel makers warn against even this, and that's certianly their perogotive.

Jim also used to use stainless steel bore brushes, too, but only as an absolute final resort on barrels that were all but gone. Occaisionally revived them enough to get another couple hundred rounds out of them, and if it didn't, he wasn't out anything.

I'd still have to put the fire lapping kits in the same category, and yes, I know of a couple of barrel makers who specifically state that using these products will void the warranty on their barrels, You lap it, and whatever the results, it's now your problem, not theirs. I'll pass.

 

[Kevin Thomas]

i would not want to shoot against kevin or david. i use jb's from time to time . i do not firelapp.

Clearly, you wouldn't be saying this if you'd witnessed the train wreck I layed down at St. Louis Benchrest's Mid Range match last week! New AR-10 and a seriously steep learning curve to be done with the new rifle!

 

[Mikecr]

If it can't damage a barrel . . . how can it help a barrel?

It won't help or hurt a barrel that doesn't need it.
It can damage a bore if used incorrectly/excess, -as everything can.

In good bores:
Where JB is useful to manage carbon(the ultimate killer of bores), Tubbs is useful to dress up lands and prolong a good lap. You don't fire the whole hail mary kit or anything like that. You just break in and run a few every few hundred rounds.

In bad bores:
Tubbs is better(IMO) at knocking out accuracy robbing restrictions and roughness, where it's a problem, than is practical with JB bore paste. You might use the whole kit here, but I've yet to hear of a barrel shooting worse after Tubb's FF. Have you?
All I see out there are reports of improvements, and baseless ramblings of naysayers.

 

[Kevin Thomas]

All those naysaying barrel makers seem to disagree with you. Call them baseless if you wish, but I'll hazard a guess that most of them have a tad more experience with the rifled barrel than most of us, and probably know what does and doesn't work. I have yet to see or hear from a single barrel maker who recommends this (fire lapping), and several who very specifically state that using this will void their warranty. Might want to talk to some, and listen to what they have to say.

 

[Edd]

Don't those barrel makers run that same type of abrasive thru the barrel when they make it?

 

[Bart B]

Don't those barrel makers run that same type of abrasive thru the barrel when they make it?

Yes, they use something like a lead or brass lap charged with abrasives to enlarge the tight spots in the very slightly undersize bore up to either their specs or those of the customer. They'll use a precision hole micrometer or air gauge to measure the diameters. When they've got a spread of less than .0001" and are at the desired specs, they do nothing else except mark the ends of the barrel blank where diameters start to flare out a bit. Those ends are cut off or reamed out by the 'smith fitting the barrel to the receiver. I think most high end barrel makers want the bore's finish to be between 10 and 15 microinch for best accuracy. Any smoother and steel tends to wipe off more bullet jacket material for some reason I don't fully understand.

Here's a good article on top-quality barrel making by one of the best:

http://www.border-barrels.com/articles/bmart.htm

Note the section on "WHAT MAKES A BARREL ACCURATE"

Softer, non-embedding abrasives, such as JB, can easily "lap" out copper wash as well as power and primer hard fouling. But these do virtually no steel removing from the barrel itself.

 

[Kevin Thomas]

Edd,

Might also add that yes, the barrel makers do use an abrasive when they do the final lapping on a barrel. An abrasive and a lot of hard earned experience. They're going to take a dim view of a customer trying to "improve" the job that they did at the shop.

Some years back there was a firm that offered an "electropolished" micro finishing treatment on "their" barrels. The original barrels were made for them by Ken Johnson, of K&P barrels, after which they did their micropolishing magic. When the marketer wanted to list them as being made by Ken, he was adamant in keeping his name out of it. As he explained it to me at the time, the barrels were "his" when they left his shop. As soon as someone (even a full-on vendor of a process such as this) does something else to the inside of those barrels, they're no longer "his" and he didn't warranty anything after that. I tried a couple of the barrels that were being marketed by this firm, and despite major claims of enhanced accuracy and greatly increased barrel life, they performed no differently than any other barrels. After hearing such claims for the past 30+ years, yes, I've become pretty jaded.

 

[TracySes23]

I personally Never recommend fire lapping is a last resort because it laps the throat and does very
little for the rest of the barrel.

The fact that the barrel shoots good the first couple of shots tells me that you need to do a good
break in.

Do a shoot, and clean after every shot for 20+ rounds and you will start seeing an improvement
on the fouling issue. It takes time and patience but is it worth the effort and improves the entire
bore not just the throat.

As you shoot, you should start to feel the improvement in the bore and the number of patches
to come clean should drop to 1 or 2.

It is not unusual for factory barrels to take more than a custom barrel so don't take a short cut
and start firing 2 or 3 shots and then cleaning. The purpose of the shoot and clean method is to
shoot 1 bullet in a clean bore and let it smooth the barrel out evenly end to end.

Fire lapping enlarges the bore at the throat and reduces bullet fit causing lower pressure and velocity.
hand lapping can do this if it is over done breaking it in only wears the high spots and fills in the
machine marks left from the rifling process.

Some custom barrels are very tight even after lapping because the barrel maker allowed for this
and reamed and rifled the barrel .000001 undersized.

J E CUSTOM

Thanks for your input on fire lapping! I've been wondering about this for the last 6 months.

 

[TracySes23]

After reading all of these posts, it appears most of you agree, it's not necessary.

3 weeks ago I ordered a Savage Model 12 LRPV with the dual port. Left port load, right port eject. I had to have it special ordered since it's not listed as a stock item anymore. As much as it costs, I want to insure I do everything I possibly can to insure I wring highest possible accuracy from it. Mine will chambered for the 22-250 with a 1 in 9 twist. Effie in the custom shop at Savage said the expected delivery date was 6-8 weeks. That was a shocker for me, since I expected 6 months or more.
Lord, I'm gonna have over $2400 in this setup by the time I have a base, rings & a scope mounted.

I'm 72 & starting to act like a kid near Christmas time.