what is fire lapping?

I believe that is the process of putting valve lapping compound on a bullet, loading the round into the chamber of your rifle, then firing it to destroy your new barrel. All it will do is cause your barrel to wear faster. Some folks do it because they believe it will enhance accuracy and make cleaning easier. It doesn't, but then some folks think C&H sugar is better than the store brand, even though cane sugar is all the same. I guess some folks just like throwing money away.
 
I, too, have some thoughts on fire lapping, but in defense, it does not use valve grinding compound, but a much finer abrasive compound. The claim is that it is a fast way to "break in" a new barrel.

Lapping, using lead slugs and abrasive on a rod, has been used for many years by makers of the finest barrels. Lapping (smoothing) the barrel removes tool marks that can cause build up of lead or jacket material, reduces the pressure needed to attain a given velocity or increases velocity with a given pressure, and may increase accuracy.

Like many other things, used in moderation, it probably does achieve at least some of those goals. Overdone, it is, as blades67 says, a way to wear out a barrel without the bother of a lot of shooting.

Jim
 
I've used it on my precision gun to very good effect. The compounds used are lab-grade, and the procedure is very specific. I used the NECO lapping kit, and followed directions. It is generally not for heavily used almost-washed-out barrels like blades67 seems to have on his rifle. The velocity is controlled (not a full-speed shot by any means), and soft lead is not used (causes excessive throat wear), only copper-jacketed stuff. Call NECO and order the instruction book, and see if you like it.
 
I remember a Monty Python skit: "Crunchy Frog"
The Crunchy Frog Sketch from "Monty Python Live at the Hollywood Bowl" and
"Monty Python Live at City Cente 1974"

Inspector: 'ELLO!
Mr. Hilton: 'Ello.
Inspector: Mr. 'ilton?
Hilton: A-yes?
I: You are the sole proprietor and owner of the Whizzo Chocolate Company?
H: I am, yes.
I: Constable Clitoris and I are from the 'ygiene squad, and we'd like to have
a word with you about your box of chocolates entitled the "Whizzo Quality
Assortment".
H: Oh, yes.
I: If I may begin at the beginning. First there is the Cherry Fondue.
Now this is extremely nasty. (pause) But we can't prosecute you for that.
H: Ah, agreed.
I: Then we have number four. Number four: Crunchy Frog.
H: Yes.
I: Am I right in thinking there's a real frog in 'ere?
H: Yes, a little one.
I: What sort of frog?
H: A...a *dead* frog.
I: Is it cooked?
H: No.
I: What, a RAW frog?!?
H: Oh, we use only the finest baby frogs, dew-picked and flown from Iraq,
cleansed in the finest quality spring water, lightly killed, and sealed in
a succulent, Swiss, quintuple-smooth, treble-milk chocolate envelope, and
lovingly frosted with glucose.
I: That's as may be, but it's still a frog!
H: What else?
I: Well, don't you even take the bones out?
H: If we took the bones out, it wouldn't be crunchy, would it?
I: Constable Clitoris et one of those!! We have to protect the public!
C: Uh, would you excuse me a moment, Sir? (exits)
I: We have to protect the public! People aren't going to think there's a real
frog in chocolate! Constable Clitoris thought it was an almond whirl!
They're bound to expect some sort of mock frog!
H: (outraged) MOCK frog!?! We use NO artificial additives or preservatives of
ANY kind!
I: Nevertheless, I advise you in future to replace the words "Crunchy Frog"
with the legend, "Crunchy, Raw, Unboned Real Dead Frog" if you wish to avoid
prosecution!
H: What about our sales?
I: **** your sales! We've got to protect the public! Now what about this
one, number five, it was number five, wasn't it? Number five: Ram's
Bladder Cup. (beat) Now, what sort of confectionery is that?!?
H: Oh, we use only the finest juicy chunks of fresh Cornish Ram's bladder,
emptied, steamed, flavoured with sesame seeds, whipped into a fondue, and
garnished with lark's vomit.
I: LARK'S VOMIT?!?!?
H: Correct.
I: It doesn't say anything here about lark's vomit!
H: Ah, it does, at the bottom of the label, after "monosodium glutamate".
I: I hardly think that's good enough! I think it's be more appropriate if the
box bore a great red label: "WARNING: LARK'S VOMIT!!!"
H: Our sales would plummet!
I: (screaming) Well why don't you move into more conventional areas of
confectionary??!!
(the constable returns)
I: Like Praline, or, or Lime Creme, a very popular flavor, I'm lead to
understand. Or Raspberry Lite. I mean, what's this one, what's
this one? 'Ere we are: Cockroach Cluster! -- -- Anthrax Ripple!
C: MMMMWWWAAAAAGGGGGHHHH!!

** For those of you watching this transcript on your terminal, the young **
** constable has just thrown up into his helmet. This is the longest **
** continuous vomit seen on Broadway since John Barrymore puked over Laertes **
** in the second act of Hamlet in 1941. **

I: (continuing) And what is this one: Spring Surprise?
H: Ah, that's one of our specialities. Covered in dark, velvety chocolate,
when you pop it into your mouth, stainless steel bolts spring out and plunge
straight through both cheeks.
I: (stunned) Well where's the pleasure in THAT?!? If people pop a nice little
chockie into their mouth, they don't expect to get their cheeks pierced!!!
In any case, it is an inadequate description of the sweetmeat. I shall have
to ask you to accompany me to the station.
H: (shrugging) It's a fair cop.
I: And DON'T talk to the audience.
Click to expand...

The point is this... I dont care about the quality of the lapping compound... it's still lapping compound that people are putting into the new barrel. This is not needed at best and detrimental on average. Just because one has used it and it hasnt screwed up your shooting - or you think you got a better group... What makes you think you would not have done just as good with normal shooting?
Gale McMillan advised very wisely against this. All your doing is accelerating the wear in the barrel... An given rifle barrel is only good for a certain amount of accurate shooting... doing this kinda crap is cutting that amount down drastically. You might shoot fine now - or even for the next 5 or 10 years... but that barrel could have lasted you 15 to 20.

The only thing you should fire-lap for are to remove scratches or pitting inside the bore. You dont do this to "Polish" the bore. You dont do this to "Improve" the bore. You dont do this to clean or remove fouling from the bore.
IF you are going to do this - make damn certain that all fouling is out of the bore BEFORE you lap it. Use FOUL OUT - or any other electonic fouling remover... Shooters Choice or what ever else you want - to make sure that the bore is PERFECTLY CLEAN free of even the slightest amount of fouling...
Then lap the barrel just enough to smooth out that scrach or those pits. Use a bore scope to check it carefully. Better to not lap it enough then to lap it too much.
 
Ross Seyfreid did some rather extensive testing with LBT bore lapping compound and new factory rifles a few years back.
The results were pretty good. The rifles generally showed improved accuracy, but the big plus was that they were polished to such an extent that they no longer fouled with jacketing material. I think average velocities rose just slighty as well - could be wrong about that.
The methods used were very specific and the compound was very fine - far finer than valve lapping compound. It was put in the grease groves of lead bullets and fired using tiny charges of pistol powder at very low velocity. He fired from 20 to 40 rounds in each rifle tested.

I don't know if it is worth the trouble to the average guy but if I had a rifle with a rough bore, I'd certainly consider fire-lapping as an alternative.
 
hmmm, I'm suprised that this works (or is doing what folks think it's doing). I do a lot of polishing to prepare samples for electron microscopy. If you used a really fine grit paper or suspension (~1 micron or less), you would indeed create a really smooth surface. However, it would take a lot more than 40 passes (probably at least 100 times as many) to smooth any imperfections. If you used a coarser grit and were just pushing in one direction (e.g. down a barrel), you'd only be creating more imperfections (scratches).
I don't know what the particulars are on the lapping compounds that are used but is it possible that folks are creating "micro-rifling" in their barrels? Perhaps that is improving accuracy.
(sorry for the rampant speculation. Would like to have a chunk of fire-lapped barrel to examine)
 
All I can say is to examine the material and decide for yourself.

My rifle was shooting 3/4-1 moa prior to lapping. After lapping with the NECO kit, it shot around 1/2 moa consistently. Nothing else was done besides the lapping. Fouling was NOTICIBLY reduced. By the way, it was a Shilen barrel and only had about 100 rounds through it (including break-in).

It worked for me. Maybe I'm just careful, follow directions well, and don't get 'creative' in trying to improve a process. Or maybe the 3 rifles and two pistols I've lapped were all flukes.
 
You must log in or register to reply here.
Back
Top