Some folks run cast bullets in their Yugo SKS rifles.
They shut off the gas port via the Yugo's grenade launching valve.
Problem is, even as a single-shot 7.62x39, the cast bullet still runs across the gas port in the barrel, shaving off a smidgen each time. Cleaning lead fouling out of a gas port is a royal pain in the tuchus. Gas-checked cast bullets tend to alleviate the problem a little bit, but the bullet's bearing surface still smears against the gas port enroute to the muzzle.
Berry's makes a plated 7.62x39gr bullet, 110gr, for $64.39/1000. I buy Golden West Brass brand 124gr jacketed bullets for my AK/SKS rifles, they go $75.00/1000. I still shoot and cast all sorts of lead alloy bullets, but not for my gas guns. It's not worth the hassle.