Weight Penalty

PMAGs are heavier than USGI.

A standard, loaded, 30-round USGI magazine is 16.7 oz.  20-rounders are 10.2 oz.

PMAG 30 RevM, 17.9 oz.
PMAG 30 Rev M2 MOE, 17.9 oz.
PMAG 30 Rev M2 MOE (with window), 17.8 oz.
PMAG 20 Rev M3, 12.6 oz.
PMAG 30 Rev M3, 17.8 oz.
PMAG 30 Rev M3 (with window), 17.8 oz.
PMAG 40 Rev M3, not weighed yet.

Those ounces add up if you don't watch them.

One reason this might matter is if I give PMAGs the Malf bonus I talked about earlier.  It changes the AWt from 1 to 1.1 for a 30-rounder and 0.6 to 0.8 for a 20-rounder.