How do the "flush fitting" 12 round LE magazines work in a pistols that use 10 round magazines standardly?

Answer 1

The magazine body has been narrowed on the inside to make a once 12 round magazine design into a ten round magazine design. In guns that use staggered magazines where the bullets are not perfectly inline but alternate slightly left and right of each other the inner diameter of the magazines has been reduced to limit the amount of left and right stagger. This in turn makes the 12 round string longer and more inline. In a same length magazine this allows only ten rounds to fit. That's why you can but kits that replace the mag body to turn them back into full capacity magazines.

Answer 2

One of 2 explanations.
1. The magazine follower is made shorter to accomodate the extra bullets.
2.The spring guide at the base of the magazine is made shorter to accomodate extra bullets.
Well, there might be a 3rd option, using a combination of both 1 and 2 above.Glock makes a +2 adaptor for their magazines, where the magazine floorplate is removed and a slightly extended one is used in its place, giving an extra 2 rounds of ammo.
HK has a "jet funnel" which is used to give a flush fit for their high capacity magazines.

Answer 3

Just to expand on the excellent answer given above, many of the 10 round pistols and magazines on the market were originally designed to hold more. Their capacity was downgraded to comply with that vile, useless "assault weapons" ban that is thankfully no longer with us. For those pistols they aren't magically creating more space, but are just using what's already there.

Another strategy is to redesign the spring and follower to allow them to compress farther. I believe this is how they get 8 rounds or .45 ACP into a normal sized M1911 magazine.

Answer 4

You can buy mag grip extenders if your pistol can accomidate them ( or were manufactured to take them)

Answer 5

boker_magnum pretty much summed it up.