Imersion correction and additions

P12 magazine to be changed to 12rnds like the real one; the addition of 20 rnd magazines for AR 10 based rifles; the addition of a 7.62x51 conversion to the NGSW-R, like the civilian MCX Spear, while making it compatible with the AR 10 mags; the correct chambering of 7.62x51 instead of 7.62x54 on the Remington-700; and possibly the addition of a Glock 20 in 10mm. The last one that one is not as important as the previous ones, which improve game imersion from the mod, but would be a nice gun addition.