Why don't you just get a LH control round feed .416???? You are spending time, effort and $$ to go hunting? Save yourself the hastle, get a LH Winchester 70 Classic in .375 or a Granite Mountain LH magnum action and make a proper (for you) .416. Going with the Win action rebarreled to .416 Remington Mag would be the most cost effective. But you will pay up for a LH .375 classic as I don't think they have made any in magnum length since Winchester shuttered their Ct manufacturing. For the .500 cal, Granite Mtn chambers the 500 jeffery that could be loaded to 2,150 FPS and meet your demands.