I'm gonna stop you right there, you just said an AR-15 is a high-powered rifle. It is obvious you don't know anything about guns and I shall ignore anything you say from this point on.
One thing to keep in mind is a .45 with a silencer will be far from silent. That is why it is called a surpressor and not a "Silencer". It will be nowhere near as loud as without the surpressor but will not by any means be quiet.