PMI Ceramic- The ceramic is heavier, too loud but has a better grouping
Diamond gt, expansion chamber.
I have used several but I find pmi to work the best.
I am a sniper and this barrel is perfect because it is quiet.
I was playing against a few friends and one of them is a U.S. Marine. I was in a prone position eyeing some enemy team members making their way to wards me. Out of nowhere, comes the Marine across my path. I shot him from about 20 feet away and he asked, "Who shot me?" That is a testimony to how quiet it is. He had no idea where I was. Similar story, I shot a guy from about 80 feet away. He didn't here or see me, so he wiped. Big mistake. I fired 2 more round at the cheater. Both hit where I was aiming; His goggles and his nuts. Testimony to it's accuracy.
Ball breaks can take time to clean. When I shot that Marine, I had a little paint in the barrel. It put a spin on the ball and it nailed him in the neck. OUCH! Keep a swab handy.
Best barrel I ever used. My theory is the same as most snipers; It takes a case of 2000 rounds to paint a bunker, but 1shot to clear it. This barrel allows me to have consistent shots, good grouping, good distance and quiet operations