Sounds like you are leaving some lube in the bore or the plug is gummed up. Be sure to check both and make sure both are bone dry and clear before loading. Start again from there and see what happens. If you still can't get a group (and you are sure of the powder), I would remove the scope andtry the irons.

Your problem accuracy is about like the BEST accuracy I could get from the one I had. Terrible! But it was a very early production model.