Hand Lapping & Cryo

[Big John]

I have done one fire lapping job for friend who does not have reloading equipment with pretty good results, although it was on an old neglected barrel with some light pitting. I dont know if I would use fire lapping for new barrels or not, I dont know enough about the process (whats all happening during) fire lapping to want to try it on a new barrel.

[ar15barrels]

I have done one fire lapping job for friend who does not have reloading equipment with pretty good results, although it was on an old neglected barrel with some light pitting. I dont know if I would use fire lapping for new barrels or not, I dont know enough about the process (whats all happening during) fire lapping to want to try it on a new barrel.

Look at Tubb's final finish system.
It's basically fire lapping but with finer abrasives.

Fire lapping uses the bullet's obturation to control where the cutting is done.
More cutting happens at the throat and the bore ends up being slightly tapered.
This is desireable.

[bridgeport]

Sounds more like an ammo issue than a bore lapping issue. When and if you do lap though, it works better to push and pull the plug as it is "scratching" the bore over its length either way and this is what you want, also it is much faster to push/pull. When I lap, I use a different/ new plug for each grit to avoid the possibility of contaminating my finer grits with embedded larger grit. Also remember that as you use the plug it diminishes slightly in size and gets
looser (a tiny bit) with each pass. Some guys finish up with fine toothpaste and or cornstarch powder for a final polish
it all depends how polished you want that bore to be. At a certain point lapping gives diminished returns though as
no matter how fine you polish, copper fouling and carbon fouling do their dirty work, but as you said, a well honed barrel certainly cleans up easier. Oh and watch your rod too as this can become grit fouled and rub oddly especially with the wood rods.

[PistolPete75]

i hear cryo is bunch of crock. any hard evidence of it actually reducing group size?

[ar15barrels]

i hear cryo is bunch of crock. any hard evidence of it actually reducing group size?

It's great at relieving stress and giving a more wear resistant surface, but accuracy improvements will depend on how much initial stress was in the barrel.
If the barrel WAS stressed a lot, accuracy would improve more by removing the stress.
A GOOD barrel blank is stress relieved during the manufacture and would usually not benefit as much (accuracy wise) from Cryo, but the surface hardening and easier cleaning would still be good.

I would shoot the barrel a few hundred rounds first before cryoing it.