Boy that all depends on how well u can get steady off the sticks. Personally I expect great groups from the bench, usually with a front and rear bag. When I switch to more of a hunting rest scenario, I don't have those same expectations. I don't have a set percentage that I compare, it's more of a consistency thing.
If I shoot my 6.5prc from the bench, any 3 shot group over .5" (@100yds) is rare and I know a flyer as soon as I hear the rifle report.
On sticks or any other comparable rest, I should still keep that group within 1.5" or smaller......at that same 100yds.
Now as it's gets out past that distance, I look for my groups to be similar to one another....that may be 3" @ 200yds, give or take.
I'm not as worried about the size of the group as long as every shot is in the kill zone of the animal I'm hunting. And for me, I'm not taking a 400yd shot unless I have a proven set up that I've practiced with and repeatedly put shot after shot in the kill zone.
In short, get to know your rifle and it's ballistics from the bench w/ sandbags or whatever gets you rock steady.
Then practice your max (and min) distances with whatever real time shooting aids you'll be using.
That's the way I go about it and it seems to give me the confidence I need to close the sale when that time comes.
One last thing...I currently use a tripod and ball head when possible. I used to get upset and worry about my groups being a smidge larger, and the fact that I would always have a tiny bit of movement when settling the crosshairs. The reality of it is that I don't need to shoot .25moa at all distances to get a clean kill.