One question.........what size bullet are you using, the 250gr or the 300gr???

I'm assuming you are using Pyro Pellets - therefore I would suggest you drop your load to 2 pellets (100gr). I've gotten good accuracy out of the 300gr Barnes in my Knight USAK using 80gr of loose 777 powder and with 95 to 100gr of loose Pyro RS Powder. If you stick with the Pyro pellets, you are pretty much stuck with either using 2-50s or else find some 30gr pellets and then you could try a 3-30gr load (90gr). EITHER load will give you a better group than the 3-50 load.