I have a Rossi 44mag carbine that has a .433 bore I would love to shoot lead through it but the lead bullets that I have tried (except the BTB .432) seem to want to keyhole. The where sized to .431. I was wondering if it would be possible to "resize" a larger, say .451 to a .434? Or for that matter if it is even practical.

That really does seem kind of large.

Nothing common (and of the right weight) is going to be real close. Even geting sizing dies that finish up at .434-.434" isn't going to be all that easy.

If i were to try, would use press mounted dies (like the Lee system), probably do it in two or thee steps. Only hint I can give is that if you completely fill the lube grooves before starting sizing, they stay open (lube..basically a thick liquid...won't compress).

think I'd invest the $ in a custom mold...or sell the rifle to a jacketed-only shooter and start over.

That is kind of what I thought. I think I will call LSI and see about having it re barreled to the proper size.

You could also try no sizing at all with a "softer" alloy. Slower speeds at first. With a "fast" powder. Might "bump-up" to the bore?

Opposite problem here. Alloy is too soft/or too much speed? One rifle in particular.
I recreate working this stuff out! It just takes time and thought.

Cheezywan

soft lead is were I would go, maybe 12-14 bhn then a faster powder hold them about 1100-1200- fps they should bump up.Then too .433 is huge for a modern bore size. I feel THEY MIGHT OWE YOU A NEW BARREL! squeaky wheel gets the grease!

Actually the bore size is .4335

Actually the bore size is .4335


How did you measure the bore ?