Larry,
Barrel wear also depends on how hot you get your barrel. If you put alot of lead down the tube in a very short while you`ll do alot more damage than fireing 10 time that many rounds a couple at a time through a cold barrel. The guy that put on my barrel say he has 1 out that the is claiming he closeing in on 2,000 rounds, and it`s still shooting bug holes.
An 8 twist in a .20 cal., interisting. Berger recomands a 9 twist with their 50 gr. bullets, is there something heaver out there???
The bottom line is if your worried about burnning out a berral get a .222, I`ve seen them with many 1,000`s of rounds down the tube and never seen one that was shot out.
I`m sure someone has shot one out, but I would hate to buy the ammo it took.