I will be receiving a 15" encore barrel in 35 Whelen Imp and wondering if anyone has data for 200-225gr bullets for this barrel length?

... I hope that's a ported barrel.... I have a regular Whelen on a Mauser action... don't believe I'd want to shoot one out of a handgun.... good luck with it. Sorry I don't have any loads for an improved Whelen.

Yes it most certainly is ported. Im rather unsure myself I may just have to wrap both hands in duct tape before pulling the trigger.