Slugged and bugged

[teddy salad]

I bought a surplus tokarev (Yugo M57 variant) handgun recently. The bore is shiny and smooth, with well-defined lands and grooves. I load it with new Sellier and Bellot 7.62x25 ammo; no surplus has been fired. The problem is that the rounds go all over the place. At 15 feet groups under 5" are non-existent. I've had other shooters try it, and they get the same results.

So I searched some forums and found that while most ammo for these guns is .308 diameter, the actual bore diameter can vary quite a bit. So I slugged the bore, and lo and behold I see .312 diameter. Time to reload.

My question is this: I have Lee dies, starline cases, and plenty of powder, but I'm not sure what diameter bullets to use. Should I just go straight to .312 (using .32 cal bullets) as some folks seem to do, or should I build up to it (.308, .309, .310, .311,etc)? Or is using anything other than .308 playing with fire?

Or should I just say "this is another reason communism failed" and assume the gun will always be inaccurate?

[teddy salad]

Thanks for the info, guys. I'll keep an eye out for some .313 bullets this weekend at the Reliant Center.