I have used imr 3031 in my 7mm rem mag. But, it is not great. The only good load that I can get out of it is 47 grn with a std primer driveing 150 grn sp. And even at that it is not what I call a good load, the only reason why I use it is that it is plentyfull around here and the good powder 7828 or h1000 is hard to come by. My favorite powder for my rifle is imr 7828 67.0 grn mag primer 150 grn etip for hunting and 150 grn sp for killing dirt. with the 7828 powder I always have consistant accuracy. My advice is use the 3031 for the small capacity cases and use the powders that have been developed for the big boys.
IMHO, 3031 in it's own right is a fantastic powder, but is not a prime choice for this application. By using it, you are opening the door for "Seconrary explosion effect". That is when the air above the powder charge burns and creates tremendous pressures above what is usual. Also, because of that air space, ignition is not uniform, and I would think accuracy would not be that good either. FWIW, I would stay away from that scenario, too many variables, and consequences.