Subguns can be much more effectively suppressed than an AR carbine in 5.56x45.
Indeed, and the reason is simply because pistol calibers produce so much less.... Energy. Compact to a fault, lowest recoil, easiest to suppress, is all great till you run into something that requires more of everything you compromised ... I think my next upper will be a 1 in 6 twist .224, 12 inch carbine chambered for 100grn frangibles, and a generic surefire can will make it work just fine.