https://youtu.be/Q0RvJP9QayY When the first carbine variants of the AR-15 were developed by Colt (the Model 607 initially, and later the XM-177E1 and XM-177E2), one of the complaints was that they were painfully loud. This should not be surprising, given the blast and concussion created by 10.5" and 11.5" 5.56mm barrels. Colt's solution was to design