I do not load for the 22/250, but with a 28 inch barrel I would be seeking the slowest burning powder I could fit in that case to take advantage of the barrel length. I am guessing the 22/250 has a tad more capacity than the 22/6.5x47 lapua that I do load. I am using a nearly full case of vv560 with the 80gr SMKs at 3300fps. I would think that the increased case capacity of the 22/250 would allow you to use something slower than RL-7, more like RL22 with the 75s. If you would like, send me a reminder PM and I will run it through QL for you when I get home.
I admit that I know just enough to be dangerous.....but dangerous at ever extending distances.