I use a old Mexican Mauser 95 with a custom receiver that was cut down and rebuilt just for the 7.62x39. I use it regularly on Javelina and Whitetails. As to the M1 Carbine....the .30 Carbine is nothing more than an offspring of the old vintage 1905 ,32 Winchester Self Loading cartridge. Poor Boy 32-20 per se....... The 7.62x39 in a proper launcher is one of the most accurate rounds in the world.
You are right that the 7.62x39 is accurate out of the right gun BUT I am looking at the knowledge level of the OP. This is a guy (no offense intended) that wants a good 'all around' rifle. He will not be reloading and wants to be able to walk into Wally World and get good ammo.
I think the .308 would be better as a "tatcticle/hunting' gun for this type of shooter.
I got a buddy who's looking at getting a .340 Weatherby for big yardage shooting. I remember you sayin' once you had a .338 Lapua...how do you think these two compare?
Thanks in advance.