This is NOT a generic endorsement of fire-lapping, just a report...

I have a Bushmaster AR-15 with heavy, fluted, chrome-lined, factory barrel that has never shot worth beans. Average groups have been closer to 3" than to 2", with the best factory match grade ammo ( premium grades of Federal, Black Hills, etc.).

I sent it back to Bushmaster and even with 3-shot groups, all they got was a 2"+ average for 3 groups. They seemed to think that was okay, and sent if back to me, unimproved.

I decided maybe the problem had something to do with the chrome-lined bore...roughness, a burr, whatever. As the barrel was generally junk for my purposes anyway (what the hell good is a .223 that shoots 2-1/2-to-3" groups at 100 yards?), I decided to try fire-lapping it.

I loaded 5 rounds with 52 grain bullets impregnated with NECO's "medium" grit fire-lapping paste; 8 bullets using their "fine" grade paste, and 10 rounds using the NECO "polishing" grade grit.

All bullets were loaded in Winchester cases, using WSR primers, and a moderate charge of VV-N133.

A "control" 5-round group was fired at the beginning of the fire-lapping session. True to form, it measured close to 3" center-to-center.

Then all the grit impregnated bullets were fired, starting with the medium grit and ending with the polishing grit bullets. The rifle action and barrel were cleaned throughly between each change in grit size.

As the firing progressed, each group shrank in size, significantly.

After the fire-lapping was complete, 15 shots of untreated bullets were fired, using the same charge weight and components. The 15-shot group size is almost exactly 1", with most of the shots clustered into one smaller hole.

Fire-lapping has not worked well for me before and, in my experience, is particularly bad for a "gain-twist" barrel. In this particular instance, however, it appears to have saved this barrel. If it had not worked, next step for the barrel was the ash-can.


Alberta Canuck

Did you get a chance to look inside the barrel before I lapping? This is the most profound improvements I have ever seen from firelapping, so I suspect the barrel was in pretty bad shape to start off with.

I'm glad it turned out so nice for you. Looks like a keeper!

Regards,
Kory

Kory -

This is one of those times I really wish I had a high-quality full-17" bore-scope... No, I didn't get a good look at the bore before fire-lapping. With my ancient eyes and 4 eye surgeries within the last year, inspecting it without a really good quality, long, bore-scope was not an option.

I did have the barrel professionally re-crowned before returning it to Bushmaster. After the re-crowning I examined the new crown very carefully under high magnification, and it appeared virtually perfect, so I am pretty sure the problem was somewhere "inside" the bore.

Thanks for the good wishes,

Alberta Canuck

Canuck, that is great result! I have read a lot of different reports on firelapping and I would say it trends toward the negative for the most part. I on the other hand have had some good improvement after firelapping. I am confident that Glen Zediker and David Tubb know about making a rifle shoot it's best and they are big fans of firelapping.

Great report! The important thing is that the process worked for you!

I think this report is a reflection of when to consider fire-lapping: as a last resort to save a barrel.

I've never seen benefits this clear. Obviously, some burr was taken down, and a barrel saved from the tomato farm. FWIW, Dutch.

So would a chrome lined barrel be soft enough
to fire lap?
Would any roughness show up on a dry patch?

Terrfic result anyway.