southtexas,
The best I can recall is Hornady introduced the Interlock feature around 1980. I was using pre-Interlock 150-grain .270 Spire Points in 1977 for sure, and know my wife started using 130-grain Interlocks when she first started shooting a .270 around 1984.
John did you see much of a difference in performance once they added the ring?
