Magazine is tight in the magwell

AICS pattern magazine wells fit differently than factory mags.  To insert the mag please try activating the mag release leaver and then insert the mag straight up and in, or, insert the mag at an angle placing the front of the mag in the front of the mag well and then rocking the back backward, up and in.  This motion is like inserting a mag into an AK47 or M1A/M14, this will give you leverage against the mag release leaver to help insert the mag.