I am about to headspace my 7.62x25. Without a go or no go guage I am going to use a live round. I have 2 types of ammo sitting around some Sellier and Bellot and some Yugo surplus from 1981. I measured several from each group and the S&B measures 1.366 avg and the surplus measures about the asme on avg. So when I go to headspace how much room should I leave. I was going to go with 2 thicknesses of Masking tape as go and 3 as no go ...will this work or am I way off?