Quoted:
main thing I look for is that the mag well would drop free the mag specially the Magpul PMAG
AR3, Interesting you mention this. I bought one of the lowers and every 20 round or 30 round metal magazine I have tried, Colt, OKay, NMHTG, CProducts, Adventure Line, slide in easily and fall out without interference from the stripped receiver.
BUT the MagPul MagLevel I tried is a push fit in and a pull fit out. It goes in and would lock, but is a friction fit, and fully loaded won't budge by its own weight.
The mag is not the same size as the metal mags when I measure it with a caliper. The mag is way out of spec. Both front to rear and side to side.
Not really a problem since I use the metal mags, but MagPul isn't drop free.
In fairness, I tried the MapPul in other receivers and it is a looser fit but barely drop free, if at all, in some. In others, it will not drop free even fully loaded, but it slides in and out easier.
It doesn't matter much to me anyhow, because three MagPuls will not fit into a 3x30 mag pouch anyhow.
Well, since you won't be using any PMAG you won't have any problems even if you picked a lower with a tight mag well.
Like I said lowers have different size mag wells, some are close to the minimum size and I'm sure there are some out of spec out there that's too small.
My LMT lower have a tighter than normal mag well, out of my 20 PMAGs only about a couple of them didn't drop free at first, but after using them several times they now drop free, this is the opposite of my three Colt lowers, one is a Match Target HBAR and two are 6721 tactical carbine, all my PMAGs drops free even when new.
I prefer my PMAGs over my USGI 30 rounds aluminum mags which some I've been using for about three decades now, I dropped two PMAG fully loaded, five feet on concrete garage floor, feed lips first (without any top covers) and no functional damage, I even accidentally stepped on one at one time and no damage.
Also I like that I could actually load it with 30 rounds while my USGI mags I usually download it down to 28 rounds so they're easier to load on a closed bolt.