Cayugad- I have a .50 Cal Black Diamond XR, and the rings/scope package from Cabelas. They are low mount scope bases, but I did not have to remove the rear sight to have it mounted. Had a local shop mount and boresight it for me...

I shoot a Black Diamond. I shoot two pyrodex pettets and the 300 grain Hornady XTP. It will shoot two inch groups but that is with open sight and I could not do any better with any gun with open sights at that range. We can't use any type of scope or optical sight in South Dakota during the muzzle loader season. We can if we want to use it during the rifle season but I didn't have a scpoe handy for that this year. I am sure it would shoot better with a scope.

Sounds good James. Wisconsin is the same way. No scopes allowed during muzzleloader season. They do allow no power red dots, and Idid think of putting a Bushnell Red Dot on the thing. I have an old Tasco Scope that I am sure will do the trick. I will use one of the other muzzleloaders I have during the muzzleloader season.... I also have some of the hornady bullets. I am going to try them today...

Actually, Cayugad, the Black Diamond open sights are laser bore sighted at the factory for the 240 xpt and two pyrodex pellets. When I bought mine, first shot was dead on at 50 yards with that combo.
Back to the original question, I found that being a little more careful with the lug screws when putting the barrel back on after cleaning will cure the issue of the stock and barrel touching. Still haven't been able to get back out to check different 777 loads.

HP I noticed the lug screw problem last night when I was cleaning it. If you tighten them too tight, you can not even cock the rifle. There is a set point where the screws allow the max travel of the striker while at the same time keeping the barrel in place. Also the ram rod needs to be in the holder when you shoot....

That would explain why it shot dead center but a little low. I will have to go back out and play somemore with it. I was shooting a different rifle today. Thanks for the heads up.

I also ordered a; Quickee scope rings and bases made for the Black Diamond today, and the extended view Dusk to Dawn Bushnell Banner Shotgun Scope for it. I figured that would be a good low powered scope to put on it. I decided I did not want the Tasco I was planning on putting on it....

I will be interested in what loads and charges are working good for you.