I had the opportunity to examine and fire a suppressed Short Barreled Sig 556 with an AAC M4-2000 can. I did not like that setup. It’s owner pointed out that the mount of the AAC can prevented the gas system from being removed for cleaning. When the rifle was fired, gas would vent from the gap between the Sigs upper and lower receivers, and blow upwards into the shooters face. Later in the day, the owner of this rifle ended up having mechanical issue with his rifle. He ended up having to take it home to disassemble it for cleaning and maintenance.
The SBR Sig556 and the AAC M4-2000 does not make for a good combination.