Bullet expansion as range increases has always been a problem.
Guys will focus on BC, then get a bunch of crawlers.
Here is the problem in a nut shell, thin jacket bullets in fast twist barrels have multiple issues. The bullet deforms the jacket(base of the bullet) when the bullet enters the lands, so in order to stop this problem, the bullet makers have to make a tougher bullet core, which retards expansion...catch 22.
So, they toughen up the jacket alloy, put in a harder core with more antimony, then add some air space between the top of the core in the bullet jacket and the HP or the plastic tip. The jacket still has to deform to allow the tip to "mash in" upon impact, or the HP has to be large enough to open up upon contact.
Making very long for caliber bullets is another can of worms. Barrel twist is huge for accommodating all shooters from high to low altitudes, cold and hot weather. Having a reamer made specifically for long throats is an investment for a gunsmith.
The only answer I have found is SPEED on a varmint bullet that will expand, and shop a credit card flat on buying good bullets when you find one that works. I really detest seeing crawlers, and coming up with a balance of speed/accuracy/needed bullet expansion is part of being a good sportsman. This speed comes at a price of often replacing barrels.
My feelings is that Dirtyhippie is correct in his analysis of current bullets and their application toward varmints/coyotes. With the Swift AI, 22/250 AI, 22/243 AI, 6 Rem AI with the 75-80g A max you have your best chances of success with long range accuracy with a good bullet expanding.
To the OP, harlanjered, we can only hope that folks will keep showing interest on long range shooting where R&D in good bullets will continue to be developed. The 87's out of a 6 Rem AI or 6/284 at 3600 is some good medicine, if you don't over twist it, and the 103-108g using R#26 is all over 3300-3400 fps.
I have a friend in NC that is shooting the 22 Grendel at 3300-3400 with berger 75g and shooting 1" groups in F class competition at 600 yards, but again the speed at long distance would retard the bullet expansion.
An answer maybe to go to a 7mm with a BC close to .800, then you have recoil to contend with.
Best wishes