One of the things I notice is the load reducing. If your load is at the right level reducing it allows the recoil to raise the barrel before the bullet exits, I have run into this several times and if the hinge is ok would suggest upping the load for a try to see if that helps lower the POI. If you are using old powder then get a new can and try it as some powders age and attract moisture.
Personally I switched too Blackhorn 209 when it came out; I had no end of trouble with 777 I live where we have high humidity most of the year on the downwind side of Greers Ferry lake and it just would not shoot good groups for me.
Also are you aware that from pellets to loose powder is not a direct comparison The pellets are equivalent to Pyrodex two 50 grain 777 pellets = 100 grains of Pyrodex and the barrel vibrations are also different.
When you switch to powder you will need to run the powder ladder to find out what the gun likes then sight in for it. At least I would expect that.
Last edited by lemoyne; 10-13-2014 at 05:20 AM.