I just bought one, I'll get some pictures of the cylinder action around the gas seal, and post them tomorrow sometime.
The cylinder moves forward when the hammer is cocked and then back after the hammer drops basically.
Just look for signs of excessive wear on the exterior, that the cylinder turns when the hammer is cocked, and that the cylinder slides up to for the gas seal.
I must not fear. Fear is the mind-killer. Fear is the little-death that brings total obliteration. I will face my fear. I will permit it to pass over me and through me. And when it has gone past I will turn the inner eye to see its path. Where the fear has gone there will be nothing. Only I will remain.