Me and another guy ran close to 800 rds thru this pair of shorty 16's today. No overheating since we took plenty of breaks although the hand guards heated up a few times. A fun time shooting down into a creek with steep banks for a good backstop, Throw something in the water and shoot an inch below it and launch it 50 feet in the air, then when it lands we both opened up on it. lot"s of fun ! Both guns on occasion would not strip the first round out of the mag when using the bolt latch, you had to use the charging handle & pull the bolt all the way back and let it fly and even then it wouldn't chamber some time. Using a variety of steel Mil spec 30 round mags with 28 rounds in each one. One gun has the M4 feed ramps , the other doesn't. My guess is that 28 rounds in a 30 round mag is just to tight. wondering what thought's are ??