If purpose built, a suppressed M4 barrel can be made essentially the same length as an unsuppressed barrel.
Ammo optimized for suppression (like the 300 AAC) makes it even more effective.
My next AR build will be 10.5” barrel suppressed by SilencerCo.
Every time I hit the range, I ask if anyone on the firing line wants to shoot my suppressed .45 XDm.
Trying to give others the silencer bug, and grow our numbers.