A have 2 sets of RCBS 7 mag and 270 dies that have different numbers on the tops of the dies. I can't find what the difference is, need some help.
On the 7mag I have a FL/seat 70 and a FL/seat 73.
On the 270 I have a FL/seat 66 and a FL/seat 87. The 87 is a small base.

What does that mean?