Great replies guys!!!
I appreciate the responses, guys. I'm going to try reducing the load to 19.5 grains of 2400 (load 10 for testing) then will do the same with 20.5 and 21.0 grains to see what happens. I will slug the barrel, as well, and see what turns up in the measurements. It could very well be that my bullets are the wrong size.
I've got a new lb. of W296 that I'm going to be working with very soon after I finish experimenting with the 2400/cast bullet combo. I also plan to try the Lil'gun later on.
Should cast bullets not work out in my particular gun I do have a good standby...its a 240 gr. Hornady XTP over 10.5 gr. of Unique. Its nearly as accurate as the Winchester Supremes in my gun but cheaper to shoot. Very low recoiling load but runs at approx. 1200 fps. Plenty of punch for whitetail.