Out to the 5, your choices don't have a whole lot of difference...especially with modern rangefinders...but the B/C difference between .264 and .277 really isn't even close.
I've killed a few elk with 6.5s, with the 140 AMAX in particular, but they've been pretty classic broadside shots. I'd imagine with a 6.5 LRX or other stout bullet, any angle on an elk wouldn't be an issue.
