Bore Lapping

[jeff223]

should it be done before shooting cast bullets?

fire lapping or hand lapping?i think a person would have more controll when hand lapping.you thoughts please and how did you do your bore?

thanks,
jeff

[drinks]

I am lazy, I just fire lap.

[Bass Ackward]

should it be done before shooting cast bullets?

fire lapping or hand lapping?i think a person would have more controll when hand lapping.you thoughts please and how did you do your bore?

thanks,
jeff


Jeff,

Yes and NO. No to abrasives unless you have slugged everything and determine that there is a reason to lap by some method.

But every time you fire any bullet down a bore you are fire lapping. Whether it has any compound on it or not.

[Bent Ramrod]

Jeff223,

First,off, I wouldn't gratuitously do anything to a gun. If there is a problem that lapping might solve, and I could get the barrel off and on easily, hand lapping would offer a lot more control than fire lapping. The chief attraction of hand lapping is that you can feel sticky areas in the bore, whether constrictions in diameter or burrs or other problems with the rifling, and give them extra attention. However, hand lapping is a rather involved process which offers the risk of discoloring bluing, possibly melting off sight inserts, and so forth.

So for my first approximation, especially if it is a factory rifle I don't want to take apart, I generally fire lap. I have a Ruger #3 in .22 Hornet which delivered fairly mediocre accuracy when I first got it. Slugging the bore showed the standard .224+" diameter, but the feel of the slug going down the bore was very peculiar; "scaly" was the only term that seemed to fit. Even though it looked smooth, the bore felt very consistently rough. It was hard to get an accurate diameter reading. I definitely did not want to take the barrel off.

I fired 80 shots of Ideal 225462, sized .225" over 9.5 gr of IMR-4198, the bullets rolled in Corbin Benchrest Bore Lap. I cleaned with a brush, solvent and patches, every 10 shots. Afterwards, a .22LR bullet upset in the bore pushed through very easily; the "scaly" feeling was gone. The bullet miked .2245" The groups of 10 shots at 100 yards started out at 3-1/4" and dropped to 2-1/2" by the end of the campaign. Good loads with cast bullets (and no lapping compound) seldom go over 2" for 5 shots at 100 yards, and the jacketed bullets frequently go under 1" for 5 shots at the same range.

So lapping was indicated in this case, and it helped. But first I determined that there was something wrong with the barrel. I have, though, never experienced a situation where fire lapping resulted in a decrease in accuracy, although sometimes it doesn't seem to have much of an effect. 40-80 shots is usually all I do.

[Molly]

There's a pretty slick method of firelapping with JB compound that's posted in the CBA (Cast Bullet Association) Forum files. Check it out.

Molly

[44man]

A lot of good advice! If you slug the bore and there are no tight or rough spots, just shoot a bunch of jacketed bullets out of it. Shoot one, clean out the copper after every shot for about 20 rounds, Then clean out the copper after about every 3 rounds for some more shots. Then make sure all copper is out before shooting cast. Some bores are so smooth you don't have to do anything, just shoot. Make sure you clean out any copper left from the factory proof shots. I would try cast first and see if they lead. Just remember you can get a small amount of leading with even the best bores. A few specks is normal.

[Molly]

Umm .... I REALLY recommend that you read the posting BEFORE trying this. It tells you how to deal with / prevent the substantial increase in pressures that can accompany the higher resistance from a bore that is coated with abrasives.

Molly