Stretch - I also shoot the 300 gr 430" XTP and 100 gr of Pyrodex P and getting close to 1" 100 yd 3 shot groups. I have a Nikon Prostafff 3-9x on my Genesis.
The only problem I have is the blowback issue. I just put some electrical tape on the scope above the cam. I wipes of easily then. And if the weather is bad I can take some off and put it over my muzzle. (Not a bad idea for any hunting rifle).