Just start at 100 and always do load develolment with no wind. You should see the clear winner at 100 yards either way. If they're pretty close, then take them out to 300. I do all my testing either at 100 or 300 depending on the rifle. Factory gets done at 100, customs get done at 300. Seating depth testing any further than that opens up a whole set of other complications and issues, mainly being the shooter and environmental conditions. I always start at .005" or .010" off and usually find a solid 1/2 MOA load or better there, so it's really not even worth testing seating depth at that point. Thats plenty good enough for hunting and banging steel. Just worked up this load at 300 yards first doing a ladder test with powder charge, then 3 shot groups at the charge nodes, all at .010" off the lands to start with, done...No need to waste anymore time and components here IMO. The group before this was .7" so both under 1/4 MOA.