I had Rem classic in 35 Whelen and had 1/16 twist and I had pretty good luck with R-15 with 225grAB load out of Nosler manual also IMR-4064.
I now shoot 35 WhelenAI use R-15 and I had it long throated for the 225grAB @ 3.500". I've shot few of the TSX 225gr and I may try some Hornady 250gr one of these days.
I had gunsmith use chamber reamers made Wilson neck and seater dies plus bushing. I'll say one thing drop and elk real fast.
I also have good supply of Rem 35 Whelen brass. I'm due to draw bear tag this coming and I got about 3 rifles I'd Iike to try plus bow and one of the rifles is the 35 WhelenAI.
Well good luck