I have a mid-length gas on both my 14.7" and 18" rifles. The 14.7" is a light weight setup, adjustable gas block, lightweight carrier, and no weights in the carbine buffer. I run an H2 buffer in the 18". I have a Sig PM400 pistol, pistol length gas system and run an H3 buffer, it was pretty overgassed so the H3 smoothed it out a bunch. I have not had any reliability issues with any of them once I got them running right at the start. None are showing any wear that I wouldn't expect. I'm sold on the mid-length gas system but then I don't really have any experience with a carbine gas system.