I started shooting a 750 in the 35 Whelen recently, no factory ammo, using my reloads, and so far about 100 rounds thru it with no fedding issues. I use a 15 year old set of RCBS dies. The gun groups around 1.5" with 225 gr Partitions, Sierra BT's, the 250 gr. Speer, and the 200 gr. Hornady. It does not seem finicky about powder choices, and I have shot groups with RL15, IMR4320, BL-C2, and 3031. It would be difficult to overload a Whelen case with any of these powders.
It is going moose hunting in September, and I think it will be using the 225 gr. Partition over 56 or 58 grains of RL15.
It is a real easy cartridge to get along with! With the price of ammo, it is easy to justify reloading gear.