Rich, I'm sorry that this happened to you. This is a terrible way to be humbled.
Have you had good luck with soft tissue shots (lungs, lower chest, etc.) at long range on elk?? I've either shot elk or have seen elk shot in the ribs / lungs at various ranges from point blank to 800 yards with nosler ballistic tips, partitions, accubonds, sst's, bear claws, bergers, sierra MK's, etc. and not a single one of them provided me with evidence that they were adequate for the purpose of quickly and humanely dispatching an elk. I know alot of guys subscribe to the theory of intense soft tissue trauma in long range shooting, which may work for things like deer and antelope, but I've witnessed a much higher failure rate in this type of shooting in an animal who can run for miles on 1/2 of a single lung functioning.
I shot a 4 point bull in Colorado one year that we saw in muzzle-loader season (late august) that had obviously been wounded by a bowhunter, and I killed it in 4th rifle season (mid-november). It came limping by me, and I dispatched it, and I called the game warden. The game warden issued me a tag for it, but not before opening it up to discover an 11" chunk of carbon-fiber arrow with a broken 4-blade broadhead inside. One lung was completely crispy green and black with no function...sounding like a paper bag crunching, and the other lung was almost 2/3rds gangrenous and filled with fluid. No way he would have made it through the winter, but he made it 2 1/2 months with that type of injury.
Having witnessed that, and also having shot plenty of elk through the lungs leaving holes you could fit a baseball through and watch them run for a half-mile I now subscribe to a different school of elk killing. I either have the ability with gun and bullet to completely break both shoulders / major bone structure, or I don't shoot.
I'd like to get an idea of what most guys are doing when it comes to ELK specifically at long ranges. I understand something in the 300 grain category could be valuable for such a task, and I also understand smaller caliber weapons with frangible bullets hitting an animal at the terminus of the spine and shoulder causing instant death as well, but you're also talking about a coffee-can sized area to hit as well. Where I hunt we simply cannot risk an elk running even 500 yards because it enters private land, or runs off into a wilderness canyon where the retrieve will be a gruelling technical climb to get the meat out. The two long range bulls I have killed were both high double-shoulders and single shot kills with Barnes TTSX. I've had the opportunity to shoot at some bulls farther away, knowing full well that I could hit body, but not both shoulders specifically, so I opted not to shoot.