For deer at those ranges, there are LOTS of great full-bore diameter choices for 1-28 barrels - everything from very modern jacketed plastic-tipped bullets that use a plastic skirt to all-lead bullets like the Hornady Great Plains, to custom cast and sized bullets, to casting your own in a custom mold.
Some of the folks who use full-bore bullets get great accuracy with them, but it seems that you have to work a little harder to get there because accuracy and loading difficulty with a full-bore bullet are critically dependent on the fit of the bullet to your particular bore - and on casting quality if you're using cast bullets. Plastic skirted full bore bullets are kind of midway between full sabots and unsabotted bullets, and they seem to combine some of the advantages of both.
I doubt that you'll see a big difference in lethality on deer, or even elk if you choose the right bullets for your sabots, the right bullets for your full-bore loads - AND put your bullets in the right places. A .50 caliber bullet that weighs 350 + grains and is made of slightly hardened lead (maybe 1-40 alloy or slightly harder) is maybe marginally better than a 250+ grain jacketed bullet if you try to put a bullet through an elk's shoulder before it gets to heart or lungs. BUT, in either case, you're best off being patient and waiting until the elk turns to an angle which allows you to take out heart/lungs before the bullet hits anything more solid than ribs.
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