Most of my "hunting " loads I work up at 200yds instead of 100 for that particular reason. If they shoot 1" at 200 then I am good to go at anything closer, and usually quite a bit further.
That said I also shoot heavier for caliber bullets in most of my loads as well. THese may or may not be in the optimum range for stability, in that particular rifle.
WHen I was working up loads for 1K, I found that while getting on paper at 100 was useful, any loads I dialed in there were pretty much useless past 400. Not that they wouldn't hit in a 6" circle, but they weren't nearly as acurate as the ones I worked up at 2-300yds.
WHen you get into shooting the longer ranges you usually looking at using a longer bullet for caliber as well as a bit faster twist to stabilize it. You are for the most part also right on the ragged edge of stability for those particular bullet at the initial velocities from the muzzle, but after 2-300yds the velocity drops and the rotational stability takes over and the bullets "go to sleep" as it's called. Once there you can easily see groups tighten up further out than up close.
My 1K rifle shoots around 2" at 100 on average, but will the same load will shoot around 1-2" at 500 if I am on my game and will group around 8-9" at 1K depending on again me doing my part. The load that I worked up initially at 100 won't even stay on target at 600 as it continually spreads out as the distance increases, but it looks good at 100.
With my 25-06 1-10 and 26-06 AI with the 1-9 twist, I shoot 120 and 130 grain bullets. THe 120's will stabilize wonderfully in my standard version but the 130's are lucky to get within 3" at 100. With the AI version, I am getting 1-1.5 at 100 with either of them but at 300 they are both down to 1" or less most times. These are being pushed to 3350 form the 28" barrel where as the 24" on my standard rig will only get mid to high 2900fps from the 1-10. They start out faster in the 28", but also spinning faster as well so there is a bit of over stibility to overcome before they settle down and fly true.
I know this was a bit much but it is the examples I have to relate, based upon what I have seen first hand.
Mike / TX