I like the 100 yard zero as well. The only thing I did not like about my SWFA 1-4 is the hashes are set up for a 200 yard zero. I am still getting the feel of it but am leaning towards a 100 yard zero and then just confirming the drops for the rest of the marks.
The hashes on the 1-4x SWFA Classic are mil based. All SWFA did was "tell" people that is a BDC, it's not. You can do the exact same thing with any mil reticle.
From center dot to first hash (maybe the gap) is .5 mil, after that it's in 1.0 mil increments.
