I've tried steel cased Hornady that used ballistic tip bullets I recall as 125 gr and having better accuracy than Russian fmj. I don't recall the diameter but probably .308. Low-flash powder, too.

I also tried Federal 125? Gr JSP. Brass cased. Accuracy was poor as they were .308 cal.

I think if you like 7.62x39 and want better accuracy and more bullet choices it's best to go with a .300 blk or .308 Win gun.

It would be nice if that improved .300 based on the .223 case caught on. .300 Hammer IIRC. It uses the same parent case & bullets as .300 but adds a few hundred fps to get 7.62x39 performance.