I thought it might be low as well but there's no sign of wear to the latching areas and it fits tight in the magwell with no play. I bought an after market no 4 magazine but it doesn't make any difference although from what I've read the magazines were "tuned" to each weapon at the factory when manufactured. I've given some thought to dressing the rear mag lips area to remove some metal and possibly allow the rims to sit high enough to engage the bolt but I really don't want to experiment with the original mag, might try it with the after market one though. The spring and follower are good and the entire assembly is clean. I have been told that a no 1 magazine will not work.