If you are going with just the one gun I recommend something like
www.shotlock.com Great for inside a closet or even a bed frame.
Another way to go is
one of these behind the door or again in the closet. Easy to install. Sized to fit in between standard studs. There are other makers that are similar. Just cut into the drywall for the right height and screws are installed inside the safe into the studs.
There is very little advantage to a pistol grip if any and a lot of disadvantages.