Re: what midrange caliber is know to be easy to load and known to have low es.
There are lots of good calibers that could fit your requirement. There are no hard definitions but I think deer and varmits at 800 yards would be considered long range by many. As long as you are not talking high volume prarie dog shooting, I will throw in my vote for the 6.5x284. I have had the easiest load development getting exceptional accuracy and tight ES in two rifles very quickly, and, had several friends duplicate the results without much work using pretty common recipes. It will flatten a deer out to 1000 yards and have no problem grouping well enough to hit a groundhog at the same distance or further with a properly chambered, quality rig. Bullet choices cover a nice range for both varmints and deer, or you can use a 140VLD for everything. Ballistics are superb, and recoil light. iMHO.
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