Obviously, the standard suppressor would be able to be removed, for various reasons. But the company that produces the SR-47, intended for the weapon to ust the KAC supressor, and so they ship the rifle with the supressor installed. The purpose of the suppressor has more to do with the intended use of the weapon, the SR-47 is a cave-fighting/CQB special applications weapon, than masking the shooters position. It's said to be unbearably loud to fire the SR-47 in an enclosed space without the suppressor in place. So it's more to do with the shooter's comfort level and accuracy, than stealthy long-range guard plinking. As I understand it, the weapon wouldn't be completely silenced anyway, as it's meant to use standard ball, ie. supersonic ammunition.
From an operational standpoint, that is, the way I've used it in-game, stealth never really comes into play. I just use it up close and mow-down everything, at full auto. The ability to use battlefield pickup magazines from the enemy, means I can hose down anything that moves, without much thought to how much ammo I use. Sure they can hear me, but I don't really care, as I can just hunker down in an ambush position, and blast whatever runs into view. I'll just stop from time to time to pick-up some magazines, and then start the music again.