Much much much less recoil. It actually felt pretty comfortable to shoot, and bruising on the shoulder is non existent (I seem to bruise at the shoulder when I shoot the 308). Was surprised that I could hold the groups tight at 200m with the buffer plus the Giessele SSA-E.
The XM80C was the only problemmatic round. The FGMM SMK's and American Eagle shot fine. With the XM80C, I believe the XM80C was under powered (for the 12oz buffer) so the rifle was randomly short stroking by about 1/2", causing it to FTF, and empty mags were caught at the BCG, not the face of the bolt. The 175gr reloads I got off my friend fired fine with no issues.
Next test - reduce the buffer weight - bring extra weights so I can swap them out at the range. Hoping to finish making the compensator too and see if I can get better/quicker follow up shots.