My Huntsman is not 100% reliable with 777 pellets either, but is with Pyrodex pellets. Pyrodex Pellets have REAL Black Powder bonded to one end of the pellet to help with ignition.
I prefer the 777 loose powder FFG for saboted bullets, FFFG for lead conicals.
You will want about 85 grains of loose 777 powder to equal your 100 grain 777 pellet load.
The pellets were made to be the equivelant of Black Powder. Two 50 grain pellets = 100 grains of Black Powder or Pyrodex by volume. 777 loose powder is 15% more energenic than Black Powder and Pyrodex, therefore you should reduce your loads by 15% when using it.
Loose powder allows you to tailor your loads to achieve the most accuracy, not to mention it is much more economical than pellets.