I have a GM-22, and while it does the job well, I have to admit that I am disappointed with it. The problem is the design for disassembly. The first time I screwed it onto my gun, I found that simply hand tightening the suppressor to the gun had also tightened the tube to the core. It was very hard to separate after that. Then, after shooting the suppressor I had to get a strap wrench to separate the tube from the core. After the second time to the range I simply can't separate the core from the tube.
The upside is that I will probably never shoot enough ammo through this thing to the point that I kill the suppressor by failing to clean it. It was hardly fouled after the first 100 rounds I put through it and the gun I bought it for isn't something I shoot a lot. But, overall, I am unimpressed. Now, Gemtech's other core suppressors (GM-9 and GM-45) seem to solve this issue by having a longer core base (due to the piston?) than the GM-22, so I am not saying that overall their core designed suppressors are bad.
What are your opinions of the GM-22?
I also have a Form 4 out for a Surefire Ryder 22, which seems like a better designed suppressor. I bought this for a gun that I do shoot, so I am anxious to get it out of jail.