I've not used a .44mag on elk, I have on many sick cattle and buffalo and many deer and coyotes, I'd trust one on elk for sure, I wouldn't compare the deer or coyote to elk, but on the cattle and buffalo I've put down with my Ruger Super Blackhawk, none have argued about it...you don't really want to get too close to sick pasture bison-they'll run down a horse in a heartbeat and kill both of you faster if they're still on their feet, I've used mine at 50yrds and under on bison and have rarely had one take more than a few steps after the first shot.

I also recommend an all lead bullet-speer gold dots are pretty sweet too, but not much beats a good hardcast in my opinion...I don't know that I'd go with a 300grn, but unless you can find an "odd man" 260 or 270grn, that's probably the best option...230-40grn is pretty light for elk.