Triple seven is in my opinion the worst propellant that you can use in a T/C rifle. The barrels are very tight and 777 makes too much fouling that is hard to remove. I am presently shooting an 80gr. load of Black Mag3 powder with the .25ACP conversion a Winchester rifle primer and a 295gr. Powerbelt non-aero tip and today I shot three in a row without a swab between and the three bullets were touching at 50 yards. I didn't shoot at 100 as I rarely shoot that far hunting. I think my max range on Elk to date is 80 yards. If you cannot find Black Mag3 try either Clean Shot (American Pioneer Powder) or Pyrodex. Stay with the FFFG grain size of all the powders. I have shot multiple loads up to three with the 209 primer using Winchester. Do not use Federal they are way too hot. I switched to the 348gr. Powerbelt and shot five shots all within a 1inch wide and 2 inch high rectangle. Same powder and same distance. Powerbelts shoot accurately and load a lot better than any sabot/bullet combinations I have been able to find. By the way 80gr. of Black Mag3 runs the 295gr. Powerbelt at about 1900fps. Plenty for Elk and should be enough for deer.