When I bought my DPMS Gen 2 Recon I bought Midwest industries HG to go on it, the shop I had do it has a hard time with the rockset on the muzzle device, to replace the barrel nut they had to take the gas block off. Once they replaced everything you couldn't pull the charging handle back, it seems they had twisted something trying to remove the MD, I had them fix it and I thought nothing more about it, until I noticed the rail protectors underneath the gas block kept bulging out after shooting the rifle.
Once I got home I looked at the underneath side of the gas block and noticed this below. It appears that I'm missing something.