By your own statement you admit you don't know if your load will push its bullet past the end of the barrel, let alone hit the broad side of a whitetail in freezing temperatures. Maybe you should confirm the performance and accuracy of your load before rejecting my advice.
Yes, I do have different powders for each cartridge I load. Actually multiple powders for each, some of which I'll probably never use again. You tend to acquire stuff after 35+ years of handloading. But it's hardly a "wasted" investment. Each one of those half-empty powder canisters represents something learned.