just for kicks and giggles tonight i loaded up 10 rounds of some 165g cast powder coated spitzers without gas checks over 19 g's of imr 4198. got 1800fps and was skipping a canning lid across the ground at 125 meters. the accuracy shocked me. makes a nice plinking round in my AR.
that was the heaviest bullet i could find data for, and it was in the Lyman cast bullet manual.
just FYI.

Not surprising. I think most AKs have a twist rate between 1/9 and 1/10. I'd like to try 200gr bullets some time.

ROT in this Radical arms ar is 1/10. just fired 20 rounds into 2.5 inches at 125m so i am a happy dog.

I may give 150's a try in my Ruger #1; it has a long throat, and can take a bit warmer loads than an AK.

i like the AK fine but so far in the AR platform the 7.62x39 shines in the accuracy dept. and just ran 30 round mag with the slidefire and not a glitch.

I think you've just started a very interesting conversation with this thread.

Always wanted a fast twist Cz in 7.62.

after a range day with a coulpe friends, i have 500 rounds now through the AR 7.62x39 with about half and half 123g jacketed and 165g cast powder coated. amazingly they shoot to the same point of aim and i have had 2 failures to feed and they followed lite charges. i am liking this setup. 30 round group at 50 yards today was 4.5 inches. that with just trigger reset and scope settling.
barrel was warm!!

If you are talking about the CZ 572, mine doesn't need a faster twist than it came with. This is my 180 gr cast load at 100 yds.

1-10 is a good twist as it's not too fast to be unfriendly with cast, but fast enough to stabilize 200's.

A 1 in 10" twist in a Ruger bolt-action will stabilize cast bullets somewhat over 200 grains.