First round though? I think most of us are biased on hit rate odds by the fact most targets we engage then get engaged multiple times once we have feedback from prior shots. It's hard to think of first round in wildly different situations off memory and think only of those scenarios for me!
I'm lucky I have some huge canyons to shoot in.
one thing I started doing to both test myself and learn from is only shoot 1 or two shots at a target (rock usually).
The idea is every shot is a "cold bore" on a new target.
I pick a target, do all the things and fire a shot. If it hits, cool. If not, why? was it my form or wind or...
Some days I'll give myself one follow up shot as a confirmer, some days I don't.
Then I pick another target with a totally different range, angle and wind situation and repeat.
I try to pick a spot that is the same size or smaller than the precision of the rifle so I can guage how I'm actually shooting.
I can repeat from the other side of the canyon or a different time of day and its all different.
That's my thought process.
I'm not saying I'm a master by any means, just that it helped me improve quickly.