Got a ton of milsurp mags from a buddy, most fit my ARs tightly and don't simply drop out when the mag release is depressed.  Can I sand down the mags, actually removing a little metal too, so they'll fit looser?  Or perhaps lightly sand the interiot of my rifle's magwell?

I would advise not messing with the lower until you've tried new USGI mags and see if the problem persists...

A word to the wise: Do not alter your receiver.
You can try working a little magic on those mags but I would leave your magwell alone.
Just my 0.02 worth.

+1 Ghostring..dont change your magwell or sand anything.If its a mag problem use them for the range and get brandnew ones for best.Mags are so cheap now there is no reason to mess with the rifle..even if they werent cheap dont mess with the rifle.Like was said try some brand new GI mags and see if its still happening..if so send the rifles lower back and have the problem professionaly corrected.

+1 on sanding the mags if you need to and leaving the lower alone.

Just wondering.... what makes is your lower?


~nb

first off, its more than likely the mags are the problem

the mag lips have been widened too much after constant use and pressure of the rnds

DO NOT mess with your AR lower

you can try this: get a vice or a C-clamp and slowly/lightly re-compress the mag lips until they fit into your lower--it should not take that much force as its only aluminum

you can try filing down the mag bodies themselves, but i would not do that either....

of course, if its not too tight and they can easiliy be pulled out (but wont drop free) then i would just use em as range mags and not SHFT mags

Like they say, don't mess with the rifle, apart from closely inspecting the magazine well and magazine release. There's not enough material in a mag body to take any sanding - it would weaken it and perhaps cause a bulge when fully loaded. Speaking of a bulge, you need to do some measuring on these mags and compare them to new, unused G.I. mags. If they're bulged, you may as well take out the followers (if green), springs (if good) and floorplates and throw the bodies away. Also, check your mag release and make sure your good mags are not binding. I think your used mags are 'sprung' - possibly part of a bad batch of mags that didn't get adequate hardening.

Try putting the top rear of the mag between two wood blocks in a vise, and just barely tightening. If the mag is still tight, repeat. Don't crush.