Some cautions on "400 yard shots" on pronghorn:

1. Make sure there's not a fence or unfenced property boundary somewhere between you and the animal.

2. Since seasons are earlier and warmer, you're going to experience distortional visual effects (mirage). Depending on the time of day, they can be so severe that you won't be able to develop a proper sight picture. Early morning is best.

3. Absolutely have a spotter with a spotting scope to identify bullet splash and watch where the animal goes in the event it doesn't drop immediately.

I can't count the number of times I've driven up within 400 yards of a herd of goats. I know lots of meat hunters who're done hunting within the first hour of the season who simply drive up, open the door, and shoot. If I were relying on goats for the freezer that's one thing, but if that's all the challenge I found in antelope hunting otherwise, I'd quit. Rather than shooting long, the challenge for me becomes seeing just how close I can get using terrain and concealment, and predicting which way they're going to be moving while I'm obscured and low-crawling through the prickly pear and sage. I've never shot an antelope at more than 200 yards, two have been less than 75, and one of those with a .44 handgun. Zero cripples.