Primary Arms are excellent people. Their optics are very reliable. I've run several on everything from my Smith .22 to an F2000 and a couple AK's in x39. Always holds zero.

The M3 is probably a better choice than the M4. Sure, the AA battery thing is nice, but the M4 also has the changeable reticle feature....this is cool to have, but its also one more part to go bad, and occasionally certain reticles sit at an angle