Accuracy has improved massively since your time for spring-piston pistols and rifles, not because of the guns, but because the pellets are so much more precisely made.

Group sizes will have halved at least, if you break out your old 1975 HW35 or BSA Mercury, it will print much smaller groups with precise pellets like JSB than even match pellets did way back in the day.

Another thing are the CO2 pistols and rifles, which add another dimension to the sport.

Tuning spring guns in your time was a opaque affair, with guesswork and myths being big ingredients. Today it has reached the level of a proper science, and you can find lots of info on this BBS about that, look at posts by 'BTDT', 'T20', 'shed tuner' and so on.

Have fun!