You are most unlikely to want .308 diameter either. Try .309 or .310.

When discussing 'hard cast' bullets for hunting I have to wonder what the shooter is trying to achieve. A hard bullet is going to perform almost the same as a full metal jacket i.e create a wound without doing enough damage to kill.

I've shot a lot of wild pigs with cast Lyman 311284 (210gn)and found that a medium hard gas checked bullet at about 16-1700fps to be an excellent killing projectile, mushrooming just like a quality jacketed bullet.

No doubt driving a hard bullet at jacketed velocities may give the desired results but it almost always has to hit bone to upset, whereas the soft bullet will still mushroom in soft tissue.

I wanted a bullet that would penetrate through massive shoulder bone and/or penetrate lenghtwise through an animal. I am restricted to using a .30 caliber rifle that is all that I have. It's a Remington 760 Pump and follow-up shots are very fast.

Talk to the guys and gals at Cast Performance and at Bearthooth, they may be able to help

You're getting good info from BA, and everyone else here. You don't need high velocity with a good flat nosed cast bullet. A 150 gr. 6.5X55 at 1600 fps will go end to end in a buck, and keep on sailing. You need to forget pretty much everything you know about jacket bullets for hunting. Different animals all together.
Load up a 180-200 gr. flat nosed gas check bullet, and move it out at 1900-2100 fps, and you can shoot right through any thing you will run into. 1900 is plenty, and probably better for the close range you would be shooting at. I live in grizzly bear country, and carry this class loads all the time up in the mountains. I'm not worried about getting ate.