I have no doubt that the 123gr Speer Gold Dot .310 diameter would work in the 300 Blackout or 30-30 Win chambered in a Contender. I don't believe the extra .002 inch in diameter would create excessive pressure issues, since the lead alloy core on these bullets is relatively soft in order to provide expansion at the lower velocities produced by the 7.62x39. I could see an issue if you were trying to push a brass or bronze solid down a bore that is .002 smaller than the bullet, but that is not the case. Of course I will throw in the normal disclaimer about start low and work up slowly while monitoring pressure signs. About the only issue I could foresee is in the event someone has a tight chamber neck and the extra .002 would cause the case to not enter the chamber all the way, or possibly not have enough clearance to expand and release the bullet upon firing. Unless your barrel has a tight chamber, I don't think there will be an issue. These are just my opinions based on what I have done to date.

Here is some work I did with my Ruger American Ranch bolt gun in 300 Blackout using the 150gr Speer .308 Blackout bullet. I'm just throwing it out there for anyone that might be interested. I was originally going to use the 150gr bullet in my 32-20 Contender, but figured the case wouldn't hold enough powder to provide enough velocity for expansion. I'm not certain of that any more though, since someone over on the 300 Blackout forum tested them down to 1400 fps impact velocity and they still showed signs of expanding. Might be worth trying, I'm still up in the air.


300 Blackout with 150gr Speer .308 Blackout bullet, and expanded bullet tested at 100 yards. Muzzle velocity approx 2100 fps.


A little hard to read, but the best load was 23.0gr AA1680 ignited by a CCI450 primer. Velocity 2114fps, group size .714 at 100 yards.


Comparison of 300 Blackout with 150 grain on left, 32-20 with 123 grain on right.

The rifle has a 16 inch barrel, so velocities in Contender barrels shouldn't drop too much.

The 32-20 is just a cute, neat, easy to shoot, cheap to feed cartridge in the Contender. I had hoped that it was capable of taking deer and other medium game at short range, and it proved that it could, although one test is not enough to declare it so. More testing is needed!