I've built a 300 blk and love it. Ejection took a little work to iron out. Now I'd like to put together a 7.62x39 on another Stephens 200 action. I'm having trouble finding a .310 barrel at a decent price and lead time, but I can get another .308 diam barrel threaded and chambered for the 300 blk. (16.5", ss matte threaded 5/8x24)

1)Would this be safe for shooting factory ammo? ( I pulled and miked some bullets and miked some new projectiles and they are all
under .310, most around .309-.3095)

2) Would fire-lapping help?

3) This barrel is 1:8 twist, would that work ok for factory(cheap steel) 123gr projectiles?
Would it work for heavier .308 bullets loaded in x39 brass? Subs and supers?

I'm thinking that this would make a nice light rifle for my Dad, who is recoil sensitive, and may feed/eject a little better.
AND just be cool and work with my suppressor!

Thanks in advance for your insights and advice.