I know of two ranges on the far western edge of Westmoreland County.
First is Crowfoot CLUB in Murrysville. They have a 200 yard rifle range, trap range, indoor pistol range, archery range, fishing pond, and a clubhouse. Drawbacks are that rapid fire is strictly prohibited (due to the multiple gas wells on property), odd design of 200 yard range, and the fact that when the trap range is open, all others are closed (except for indoor pistol). The 200 yard range goes downhill to a pond then uphill. If you are trying to shoot 50 yards you are up on the rifle to get it aimed right while sitting at the bench.
The other is some type of strictly trap range on 286. Its a public range but only offers trap shooting.