As JB said, no hard fast rules unless you are shooting competition.
I have had #1s shoot sub moa out the box.
1885 Low Wall 243 all day 5/8-3/4" at 100. Shot first 2 inside a half inch at 200 yds in a 3 shot group......
#1 243s, groups 3/8" out the box first 3shot group, a 1A, another RSI mannlicher shot around 3/4-7/8" out the box. 1B 25-06 7/8" factory WW 120 OPE. 1B 270, not so lucky, 1-1.5 moa after bedding stock, but I digress, it was a pre-Ruger mfg. bbl, and outsourced bbls back then were hit/miss.
The 1A above, got a 6BR custom via Pac-Nor, one calm cool morning I shot 3 shots at 330 yds, yep, and the group was UNDER 1/2"......at 330 yds. Inherent? Certainly the action had the potential to allow a good barrel in a good chambering consistently spit those bullets out TIGHT.
Single shots can be fickle, but I have been pleased w/hunting accuracy out the box. My current, a K1A 6.5x55 put 3 into 1.1" at 200 yds. It's a routine sub moa......but Paul said, I never shoot a group into an animal. One good hit, on the first try is my goal, and usually what happens when I do my part.
BTW, those Singles, groups aside, will in MY experience as many other guns, put their first shot from a cold bbl where I want it to go, time and again. Bedding affects groups no doubt as every rifle is independent. But first shot cold bbl accuracy is my #1 concern in sighting in, and when it counts, for big game. I enjoy paper, but my primary end point is taking game with single shots.
FWIW, my longest kill on deer was with that 6BR, right at a pre-lasered (furthest edge of the field I hunted where the deer was by the fence adjoining a refuge), 400 yds. Accuracy was never a question as that gun was proven accurate, consistently and I knew where to hold. My oldest boy shot his first and longest w/that Low Wall above, broke a deer's back at around 300 long paces.
Single shots are fun......even when hunting w/bolt repeaters
Make all your first hits a good one whatever you use! Esp. on big game. If not, accuracy in groups will often be moot.
Big Whoop, if you have yet to try one, decide what model and caliber you want and TRY one. You might be happy you did.
