I have taken some big game at over 400, out to around 550--several before laser rangefinders appeared, when I'd stolen from previous gun writers (especially Elmer Keith) how to use a scope's reticle--or even a front sight--to provide a pretty good "measurement" of range as long as I knew the approximate chest-depth of various animals. It worked well, but a laser works better, unless of course it doesn't provide a read-out, which is why I still keep up with my reticle-ranging.

But haven't shot one over around 350 or so for a few years, mostly due to not doing as much "trophy" hunting. So far haven't been tempted to stretch the range to 400 when making meat. But will also point out that anybody who shoots enough smaller varmints at longer ranges to consistently hit them over 400 won't find killing deer-sized game much of problem. Remember one day under somewhat unusual prairie dog conditions where I killed 9 of 14 at 600-650 yards with a 1-12 twist .223 Remington using 50-grain Ballistic Tips. If you do that sort of shooting regularly--especially with a big game rifle, which I've also done--400 isn't a problem on a pronghorn.

“Montana seems to me to be what a small boy would think Texas is like from hearing Texans.”
John Steinbeck