I’ve killed dozens of elk and seen another dozen or so killed (most with a 300 mag( win and wby) and a 338/340by. Most shots have been between 300 and 400 yards. My gun of choice is a 340wby, and if I didn’t have it, my old 338. In my experience, the 300 mags shooting non premium bullets (corelocs or Interlocs) kill a touch faster than the 210 partitions I prefer in .338 bullets. When the 300s were used with partitions, there was no discernible difference. I prefer the bigger slugs because even at range, there’s never been a doubt about having hit an elk. I can’t say that about the 300s. I also prefer the the heavier partitions because I can use them at point blank range and not worry about busting shoulders or raking shots like I would if shooting non premium bullets. Recoil? In my rifles, I’ve always found it to be sharper in 300s. Trajectory? When sighted in 31/2” high at 100, out to to 400 yds, there is not a difference that will ever be noticed in the field. Accuracy? My Mark V and Ruger 77 alway shot exceptionally well (factory loads for the 340 and handloads for the 338). I’d be comfortable shooting either caliber for the rest of my hunting days. Given a choice, I’d always pick the bigger diameter. Just my 0.02.
