Change is good.
Mine is nearly all NFA, and it has been flawless with standard 115, 124 or 147g ball loads, and even some 124g HP's. But last weekend I was shooting it and got a double fire, and then another one that went off as the bolt was out of battery. This was with the Winchester white box "NATO" rounds from SGA Ammo, (supposedly 10% hotter but not designated +P). Went back to the Speer Lawman 124g, and had no more issues.The buffer you can experiment depending on your loads and what you are trying to accomplish. Alot of the 9mm buffers are solid and depending what you are doing can get alot of bolt bounce. I think I have thrown in some H3's with a Wolff 25% stiffer recoil spring on some. Others, just the H2 or H3 is fine.