RE: Hornady SST Slugs
Most of the modern sabot slugs should work fine for you, the key is to find the brand that works in your gun. And (I believe most will agree with me) not your make or model, but your gun. The problem is, that can cost a lot of money at $2+ a slug (Hornady, Remington CorLokt, Federal VitalShok, etc).
I personnally sight in at 100 ydswith a bushnell holosight, no magnification. For sighting in, I use whatever I can find that is cheapest, (typically a Brenekke, purchased at a gun show). I then use what works best for me, which is the Federal VitalShok slugs with Barnes Expanders. They have a good flat trajectory and good retained energy. I shoot a 3 shot group and adjust if necessary (not usually). I like the 2 3/4 inch with the 3/4oz slugs.(Federal also has 2 3/4 and 3 inch versions with 1oz slugs).
Anything inside 100 yds, I aim at the kill zone and know that I'm within 2 inches.No deer can survive that. Here in central Iowa (as probably in PA), it is unusual to take a shot outside 100yds.
At 300 grains, the slug you mentioned is essentially 5/8oz, typically a 20 ga slug. You didn't say whether you were shooting 12 or 20 ga.
I just realized that this is long winded and maybe rambling. In my opinion...if they shoot well for you, use them. From 100 hunters, you'll get 150 opinions.
Bottom line: No deer can survive any slug within a well aimed 12 inch diameter circle within 100 yds from a good slug gun and a steady (well practiced) shooter.
Happy Hunting.