We used to issue them for a specific use.
The ones that ran, ran well enough I guess, but about 40% of them would NOT run reliably in all of our rifles, so given the weight of load out, and the factor of losing say 50 rounds or so if the Mag got dropped in favor of a 30 round mag in a emergency reload, we ditched them. Still have them in the armory, covered in dust.
Cleaning and lubing the things is a PITA so it didn't bring a tear to my eyes, and they did stress the dickens out of the mag catches.
For a fun toy I love 'em!!!
Just hit the fun switch and melt the handguards off!!:D
Just my .02
E4E