Conceived by Veral smith, IIRC, fire lapping consists of shooting light loads of soft cast bullets, impregnated with a very fine lapping compound. This can remove many of the fine microscopic burrs left by the rifling process in new barrels. These fine burrs can remove tiny bits of bullet jacket material and lead to fouling of the bore prematurely. Some premium barrel makers use this method of lapping their barrels
I have an elderly Long Lee that had been crudely sporterised but has a relatively clean exterior. The bore was worn and had fine pitting throughout its length and lizard skin for the first few inches ahead of the chamber, showing that it had seen a bit too much cordite ammunition over the decades. I recently found a bottle of .303 bullets that I had treated with Veral's paste a couple of decades ago. I shot them with a small powder charge, two rounds at a time, and then cleaning. I did this for 40 shots and fired 5 shots of my current load at 0, 10, 16, 30 and 40 lapping rounds. 5 round group size and the best 3 shots are indicated. [50 yards]
Lapping round......................5 shot.................................Best three
number...................................group..................................shot group
0.............................................6 & 5/8..................................1 & 3/8
10..........................................4 & 1/2..................................2 & 1/4
16..........................................2 & 7/8...................................1 & 1/4
30..........................................2 & 7/8..................................1 & 1/8
40..........................................3 & 3/8..................................1 & 5/8
Though the lapping has shown a definite improvement, it seems that I may have reached the improvement limit for this rifle. OTOH, the front sight is a bead type which gives me the worst sight picture and there is a large chip forming in the butt stock at the receiver, so the deck is stacked against me from the start.
After firing the first group, there was noticeably more resistance to cleaning and patching in the last few inches at the muzzle. It seems that I was just running out of lapping near the muzzle. It was after all a Looong Lee with a 29 inch barrel. This effect continued throughout the test but overall resistance decreased as the testing progressed.
So fire lapping is a successful technique, both for increasing accuracy and smoothing out the bore to reduce fouling. I will probably try another 10 lapping rounds, as well as installing a post or globe front sight and check the stock fitment. I might even try a Parker 9F rear sight. It's all part of the fun.
Some people have objected to fire lapping, saying that it erodes the bore excessively. I'm posting photos, in order at 0, 16, and 40 lapping rounds, of the same spot in the barrel. There is no apparent difference although there seems to be a bit more shine to the bore since I started, but that could be totally subjective. Merrill Martin, in Precision Shooting magazine, has written that he has found diamond paste to be a better lapping agent. I have used it, but not enough to give a valid opinion, although I will use it in the future.
I have an elderly Long Lee that had been crudely sporterised but has a relatively clean exterior. The bore was worn and had fine pitting throughout its length and lizard skin for the first few inches ahead of the chamber, showing that it had seen a bit too much cordite ammunition over the decades. I recently found a bottle of .303 bullets that I had treated with Veral's paste a couple of decades ago. I shot them with a small powder charge, two rounds at a time, and then cleaning. I did this for 40 shots and fired 5 shots of my current load at 0, 10, 16, 30 and 40 lapping rounds. 5 round group size and the best 3 shots are indicated. [50 yards]
Lapping round......................5 shot.................................Best three
number...................................group..................................shot group
0.............................................6 & 5/8..................................1 & 3/8
10..........................................4 & 1/2..................................2 & 1/4
16..........................................2 & 7/8...................................1 & 1/4
30..........................................2 & 7/8..................................1 & 1/8
40..........................................3 & 3/8..................................1 & 5/8
Though the lapping has shown a definite improvement, it seems that I may have reached the improvement limit for this rifle. OTOH, the front sight is a bead type which gives me the worst sight picture and there is a large chip forming in the butt stock at the receiver, so the deck is stacked against me from the start.
After firing the first group, there was noticeably more resistance to cleaning and patching in the last few inches at the muzzle. It seems that I was just running out of lapping near the muzzle. It was after all a Looong Lee with a 29 inch barrel. This effect continued throughout the test but overall resistance decreased as the testing progressed.
So fire lapping is a successful technique, both for increasing accuracy and smoothing out the bore to reduce fouling. I will probably try another 10 lapping rounds, as well as installing a post or globe front sight and check the stock fitment. I might even try a Parker 9F rear sight. It's all part of the fun.
Some people have objected to fire lapping, saying that it erodes the bore excessively. I'm posting photos, in order at 0, 16, and 40 lapping rounds, of the same spot in the barrel. There is no apparent difference although there seems to be a bit more shine to the bore since I started, but that could be totally subjective. Merrill Martin, in Precision Shooting magazine, has written that he has found diamond paste to be a better lapping agent. I have used it, but not enough to give a valid opinion, although I will use it in the future.
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