J.A. makes a good point about the chrome bores. Sounds like a good project for a Yugo SKS, as it has no chrome lining. The added weight up front with the grenade launcher/sight also would tame the added recoil of the heavier bullet. The Yugo stock is also heavier and stronger than the Chinese version. With the gas-valve, you might also work up an adjustable system to tune it for your load. Just a few more ideas. (I like the Yugos.)