John Moses Browning. (Doffs hat). That thing is coming up on 100 years old and we’re talking about it as the best alternative (which it is) to a 21st-century problem. Oh, yeah, and I shot a 1911 today. 106 years on that design. Kalashnikov was a baby by comparison. Glad I’m not a firearms designer...
The only things you gotta watch with that puppy are headspace and timing (easily done with a few minute's training - or by using the new FN barrel change system that doesn't require it), making sure that it is properly lubed, and keep the bursts short/change the barrels every 400 rounds or so.
Those dumb little skiffs will disintegrate at ranges far beyond small arms/RPG reach.