Me too. Freepers have the best gun advice.
I regularly shoot an 11.5 inch with HBAR barrel, 5.56, using a holo sight. The gun has a CMMG piston kit and I had to take half a coil out of the buffer spring to compensate for the reduced dwell time, but recoil is almost non-existant without a buffer tube recoil piston, so I doubt I would add one.