With full power loads, you're right up there with .357 Mag. ...Maybe even .30 Carbine.
It has some bark.
But, as I've said many times before in this thread....
I, personally, don't find it anywhere near as offensive as .357 Mag.
Firing it without protection will make you regret that decision, but I'd rather run a cylinder full of .327 Federal through my GP100 without hearing protection than run a cylinder of .357 Mag through my brother's GP100 under the same circumstances. (The two revolvers being identical, other than finish and chambering.)
And to sort of, almost contradict myself....
If I was carrying my GP100 with full power .327 Federal loads, in an area and season when and where it was legal to take an upland game species with the revolver, I would pass unless I had one of my .32 S&W Long or .32 H&R loads available.
I value my hearing.