I own the same gun, its rated for 109gr of ffg powder and 1 1/2oz of shot! I built mine from a kit a couple months ago, and i love it! Mine doesnt have screw in chokes, but rather a cylinder barrel, and a modified barrel. Ive shot it many times thus far, ive worked up a "General" game load that consists of 90gr Pyrodex RS, and 1 1/4oz of #6 shot, should be bad medicine on pheasants out to 35yds. I did play around with a turkey load for it, and i would go with 105gr Pyrodex RS, and 1 1/2oz of buffered #6. The cylinder barrel would be my <25yd barrel, and the modified my 25-35yd barrel
It throws an even pattern with that setup, i have yet to try 10ga plastic shotcups in it, but intend to. One heads up though...most 10ga shotcups will accept more lead than what the gun is rated for
Id get a scale and begin cutting down a shotcup in length until you get to where the shotcup is coming in at 1 1/2oz when topped off. They measure and remember that length, or cut a bunch right off the bat