I'm going through gas rings on one of my carbines every 2-3k rounds! WTF? I've tried everything; replaced bolt carrier, replaced bolt, replaced rings with a different type, changed ammo. Only thing left I can think of is the gas tube or gas block - but what is it that causes this. Doesn't happen on any other rifles I have or have ever had. It's a carbine length system on a 16" barrel.