Not much. That's because over the years of shooting at rocks, I've learned that in the field, at least in the mountains and deserts here in the west, the wind can do lots of tricky things.
Your elk at 400 yds. would have to be holding still with less than 3 mph wind and it would have to be in a steady direction. On top of that, I'd need to range him with a LRF, and have a solid rest to shoot from. Above all, I'd have to have field tested the load I was using at said distance(s) in such a wind....
I might be inclined to shoot at a deer more readily simply because they die easier than the big tough animals with a less than good hit.
The other thing is that if he's holding still for all of the above, he probably doesn't know I'm around. Therefore, I can try getting closer. Yes, you can get closer even across open ground. I've done it with both elk and pronghorn. E
Less than 3mph of wind?
How many elk are you going to find on the surface of the moon?
Dave
