Reliable 30 rnd. mags= necessity. Sometimes carbine mags are more finnicky than AR mags, and the inconsistencies in non-military guns doesn't help matters. I can personally recommend any of the GM carbines and Winchesters, but the latter are getting awfully hard to find. I personally favor the adjustable ramp over the earlier aperature as well, but I s'pose that can more or less be a matter of personal preference. You get a bit more precise zero, but the ranges marked on the sight are for this little gun, well... academic. More abstract, really. Shooting the carbine over 200 yards requires previous experience with mortars and other things similairly high-angle.