The tighter the two halves are the better for sound reduction. not as much blowback. also you can get a charging handle that releases gas to keep it from hitting you in the face.
I had a gun i was going to buy there a while back, was 3% credit card fee, some charge zero percent but when i seen they want 100 bucks to ship this gun i immediately dropped that. last one i ordered was only 18 bucks.