It took me awhile to work a load up in my CVA .45 - plenty of trial and error. Couple tips - start at a lower powder charge, 80 grains and then work up. Try switching primers- I found that for whatever reason, federal primers shot much more consistently than the kleenbore primers I had been using. CVA's tend to like powerbelts forsome reason- so that might be an option.

225 grain Powerbelt + 80-90 grains of 777 should give you good performance out to 150 yards.

If you're set on having a flat-shooting 200 yard gun, you'll probably need to stick with shockwaves, dead centers, or something along those lines. But if you can't get them to group, then I would suggest ditching them for something like a 225 or 275 grain powerbelt or 200 grain XTP with a lower powder charge and limit your shots to 150 yards.