fire lapping

[johndhammer]

hello:

my grandfather was really into guns and hunted until he died at age 72. he would buy,and trade them all of the time.

when he got a rifle that was inaccurate, he would "fire lap" the bore. this consisted of using "clover valve grinding compound" (fine) and coating the bullet of a live round and firing it from the rifle. he would do this alternating between coated rounds, and three non-coated rounds until the rifle shot to point of aim.

has anyone else heard of this? or was he just a "crazy old man?" (i don't think it was the latter)

bj

[Doble Troble]

Not crazy (at least regarding fire lapping). Here is a recent thread from the AR site that provides some info: Link to AR fire lapping thread

[MorgansBoss]

Certainly not a "crazy old man", well not for this anyhow. Fire lapping is an established practice, as is simple "bore lapping" done with a cleaning rod and bullet, plug, tight fitting patches or brushes. Personally though I consider it a last resort as in any polishing process you are removing parent metal. That is to say you are making the bore larger - even if only by microns - and that is not necessarily a desirable thing.

 

There is a place for this procedure in the arsenal of gunsmithing tricks, but I would not consider it as THE thing to do to every poor shooting rifle. Start with the simplest cure and work up until all easier to fix problems have been eliminated.

 

There are companies who sell fire lapping kits. Maybe grandpa should have went into business!

[Spiris]

I'd like to chime in here as I have had a good experience fire lapping a rifle. I had heard about the procedure and I had a good turk mauser all original that had a good muzzle fit

on 8mm bullets. The bore was dark but with good rifling. I had cleaned this bore with at least a hundred patches and tried all sorts of cleaning fluids and soaks and brushes, but the patches were always dirty, never could get it clean. It would group around 4" with handloads, worse with Turk military at 50 yds. I had some 320 grit lapping compound and made a little mix with Alox lube and coated 5 rds. and let it dry. Loaded some Rem. cases with 30 gr. of surplus turk powder and coated Turk bullets and shot them at the range. I cleaned the bore and noticed the bore started to shine up a bit. The next 5 rounds of 170 gr. Speer handloads was around 2" at 50 yds., a noticeable change. I have not tried Turk ammo yet, but I'm expecting a difference there too. It worked for this situation, but I personally would not use this procedure on a commercial barrel. Hand lapping only as a last resort. The crimp ring on the pulled Turk bullets allowed the mix to stay on the bullet when loaded. Hope this helps.

 

Spiris

[MorgansBoss]

As an after thought... I used to be involved in small-bore target shooting. A lady at the club had an older M52 Winchester that had started slightly losing its edge. Envying they guys shooting top scores with Anshchutz' she decided to buy one - trading-in her Winchester. The guy handling the deal lapped the barrel (a 1" SS Hart) before I bought it from him. The first time I shot it competitively was in a bottle cap match where my son and I each won with it! She was visibly upset. A week or so later we beat her score again (badly) in a regular bench rest match. She was really upset with the guy who had sold her the new rifle (and me her old one). She finished the season but hasn't competed since.

 

So yes, barrel lapping can make a difference. Just be careful not to do it to a poor shooting gun you've bought from a friend, then shoot against him!

 

BTW - after several years that particular rifle once again began losing its edge. Did I re-lap it? Absolutely not! I sold it.