I do know for a fact that you can't use the low output primers that you'd use with 777. You should use a standard shotgun primer. My encore can shoot 12 or 15 shots with sabots before it get hard. I tried this intentionally just to see if what they advertise is true and it is. With powerbelts you should not have a problem. I just use the standard Winchester 209 primers and it works very well.
Let us know how you make out, keep us in the loop.
Thanks and God bless