The whole rifle and caliber is the best in my own custom seeking mind of the "best" air rifle (Springer) and caliber (.20) so I had only ONE rifle customized in air:
The Hector Special in team with Lothar-Walther to make a run of .20 L-W barrels for the D54.
The other "non" customized rifles in .20 I have are: HW50/HW80/HW97/HW98.
The "first" I guess was the Sheridan Silver Streak with pellets that came out of plastic yellow boxes.