I have done extensive testing with my Encore 209 x 50 over the past 5 years. I started my muzzle loading with a Knight BK-92 with black powder in the fall of 1992. When I went to the Encore and T-7 with the 209 primers my accuracy was horrible. The Knight ran circles around this barrel powder combo. It did not matter what bullet, sabot or caliber I used there was no accuracy. I read and researched everything I could find, I even went as far has have the QLA cut off the end of the barrel and had it recrowned to see if this was miss aligned. It ended up making no difference.
I purchased a new 50-caliber barrel two years ago, with T-7 my accuracy was like before, horrible. When I say horrible I’m talking 6-inch group at 100 yards with just about any bullet / sabot combination.
When Buckhorn 209 came out I ordered it and put it through a variety of trials. I ordered in new sabots from MMP + their magnum sub base in .430, .452, and .458. I used Hornady, Sierra, Barnes and Hawk bullets.
I shot up two canisters of BH-209 over the course of a weekend. The easy answer is BH-209 is the ONLY powder I will ever use in my Encore. I will never deal with Triple 7 again, BH-209 gives excellent accuracy no fouling easy to load shot after shot.
Some bullet / sabot combo did better then others. The .430 & .452 caliber were the best while the .458’s were wide groups.
My pet load is 120 grains of BH-209 with a MMP high-pressure sabot (HPH-12) with a 275 grain .452 Barnes that is designed for the 460 Smith & Wesson and CCI-209 magnum primers for 2068fps. I contacted the makers of BH-209 (Accurate arms powder company) they recommend using 209 magnums for solid ignition. I also found no need to use the MMP Magnum sub base as it did not seem to make any difference.
Now with that said, my cousin has a CVA Optima and we tried BH-209 as I did with my Encore. We had hang fires and poor accuracy. We concluded the CVA was not designed for BH-209.
Hope this helps.
B..