I have used Pyrodex and BH 209 and now use 777 and 777 is the most accurate powder i have used in my encore and i can use weaker primers that are easier on my breech plugs and easier to ignight so Its a win win or me with 777 . And ''ALL'' our sporting good shops here in town sell it and its cheaper than BH209 . Its $24.00 for 1 lb of 777 and 38.00 for 10 oz BH209 here . I bet all you need to do is go up or down a little with the amount of loose 777 and you will get her dieled in !!

Two pellets of 777 are roughly equal to 100gr of Pyrodex or 100gr of ? Black powder about like GOEX FF. or 85 gr of loose 777 or 78 gr of Blackhorn.
If you check it on a chronograph and there is the velocity difference that you think then the 777 has either drawn moisture or set on the shelf to long.
Never have had those problems with Black powder, Pyrodex or Blackhorn.
I did have them with APP and have heard of them with 777.