Fire lapping scares the cr*p out of me for the same reasons mentioned above. I think I read some where that to use the product properly you want to do it, then rechamber to a longer cartridge. I think I read where it does most of the "lapping" in the throat area and diminishes down the bore, but not sure on that. I have polished quit a few bores with satisfactory results. It takes a lot more time and effort. How ever I have not ruined any throats doing it. I do it by getting a slightly under sized brass brush and wrapping over sized patches around it, until it is tight fitting, barely can get it down the bore with polishing compound on it. I then coat it with a metal polishing compound. Do not use any thing real aggressive like valve grinding compound. I have used Mother's metal polishing compound, Flitz and JB bore bright. I stroke it at least 100 times. It gets easier to push your cleaning rod through as you work through the 100 strokes. If it gets too easy, I add another patch on top of the ones already there. I also add a little polish as I work, making sure there is a generous amount on the patches. I stroke it so the brush with patches on it does not go all the way through (out the bore) and pull it back out into the chamber, then push it through again. I use a bore guide for this so I do not damage the throat/and start of the rifling. If you push it out too far and it comes out the far end, detach the brush and start over at the chamber end. You do not want to mess up the crown + it will be very difficult to pull it back through. If the brush/patches are fitting tightly like they should, your arm will feel it after 100 strokes. It is so tight that I have to use both hands, one pushing and one on the rod to keep it from bending until I get well into the bore. Depending on how bad the bore is, I may elect to give it 100 more. I have found this reduces the break in period and helps smooth up the bore so it does not foul as quickly. As far as accuracy, I think it helps a little, but not by a whole lot. Where it really shines (pun intended) is in the clean up of the bore. I had a cheaper after market barrel that was very rough on the inside. It would shot around .5 or a little more at 100 yards for the first group, the second one would open up to .75" and from there it went South really quick. I would clean up the bore and the same thing would happen. I started to polish the bore as described above. I gave it 150 strokes, then shot it 20 rounds. I would then bring it back in and polish it again, then shoot it again. I kept this up for maybe 6 or 7 cycles, a lot of work. The pay off? I can now shoot it 20 rounds with out any copper fouling at all. It will shoot under .5 MOA and some times under .3 until I get up around 50 rounds or so then, accuracy starts to drop off little by little. BTW make sure the bore is completely clean - no copper fouling - before each polishing session and you throughly clean the bore after polishing before shooting.
