I guess they are capitalizing on the fact that HK won't make a civilian MP7 (more like legally can't) and built an AR that takes the round.

A full 40 round mag weighs just over a pound.

Will go on a standard lower with no need of a mag adapter.

Sure...hipster...but still...I bet fun as hell. Cue the haters.

https://cmmg.com/four-six