Its not about force. I can insert the mag slowly up until the baseplate contacts the frame pushing on it and it often still doesn't seat until I "jiggle" the mag body a bit. If I slap one in quickly no matter how forceful about 20-30% of the time it falls right back out of the gun. Like I said I wouldn't care about carrying such a mag IN the gun to start with. Once it locks in its no problem, but I wouldn't carry one on my belt as is.

Swapping the SD baseplate over to those same Sigma mags totally alleviates the issue (I've already tested this) - they seat easily and correctly every time. I've got 3 Sigma mags and 2 SD's, but I'll swap SD baseplates over to the Sigma mags as soon as they become available for sale separately (not sure why but Midway nor Brownells have an SD parts category yet).