Unfortunately Wilson type cartridge headspace gages are not available in the US for the 7.5 Swiss. Headspace gages have not been available either until just recently. Midway had PTG made 7.5 Swiss chamber headspace gages. http://www.midwayusa.com/product/224...5x55-swiss-cip
So, I too have been using a comparator. The Swiss round has a very steep shoulder , which is an excellent design for automatic weapons as it provides a firm stopping point , however the steepness makes deciding which Stoney point gage a bit tricky. I ended up using the D4000 gage.
I like Bart’s advice about rotating the case or smoking the case, though I think rotating the case will be difficult as the Schmidt Rubin action has a unusually deep receiver ring. I can’t get my fingers on the case in my rifle. There is always the chance that your dies are insufficiently sizing the body of the case and you have an interference fit near the case head.
I set up my sizing dies with the Stoney point and the rifle chamber. I bump the shoulders back until the bolt closes, then add a little (like 0.001 to 0.003). You will just have to monitor your cases to see if you are developing case head stretch.
By the way, in my testing my 7.5 Swiss rifles liked 4350 and 175 grain bullets.