Steve,
I'm a firm believer in modest cartridges like the ones you mentioned, and some others as well. I'm on my second Grendel, the first not being quite what I wanted. Have yet to shoot anything with it, but its ballistics put it within striking distance of the original ballistics of the .250 and even the .243, but with great bullets like the 129gr ABLR and 120gr Gold Dot. Leaves the .25/35 in the dust, except maybe for the panache or cool factor. It's been decades since I took a whack at a deer at over 100 yards; the places I hunt just don't offer such shots. While I've not clocked it yet, the load I'm working with now, the Gold Dot over a near-max load of PP 2000MR, zeroed at 100 yards is only about 1 1/2" low at 150, and doesn't fall below 1000 foot pounds of energy until 325. Velocity remains above 1800 past that. Actually, the load data shows it going somewhat faster than the 2500fps I used for my figures, but I went with the lower number to adjust for my slightly shorter barrel. The point of all this is that with good bullets and good shooting, the modest cartridges deliver plenty of deer power, while using about 2/3 the powder, and with very mild recoil and potentially long barrel life. I put the 6.8, within the first 200yards or so, in the same class, with the Russkie 7.62 a bit behind.
I've been thinking about a 6x45 for a while, but with the ARC out there, I'd go with that now, probably in a Howa, but maybe in a TC barrel. A lot of 6mm bullets have wandered into my stash, so it makes perfect Loony sense to get something (other than my .243 and 6CM) to use them up.
