For a mild load you might try 8 gr. of Unique under a 250 gr. Keith-style SWC that is sized correctly for the throats. Should give close to 1000 fps in a tight gapped gun like that. To step it up a notch, a starting load of HS6 or 2400 has always worked well for me. For full throttle stuff 296 or 2400 get the nod. I can't help with factory loads.