T/C White mountain Carbine?
 

Just bought this gun not sure how much load grains to use and what is your thought about this gun. It is a 22 inch 1/32 twist barrel and im going to shoot 270 grain powerbelts platinums out of it.

Up to 100 grains it should be fine. If the powerbelts don't work, try some T/C maxiball. Or of course you could try some speciality conicals.

Mine shoots well with 370 gr Maxiballs and 90 Gr loose Pyrodex RS. There are lighter and heavier Maxiballs, but not sure how available they are.

No reason not to try Hornady FPBs. They may shoot well with that twist.