I sold off my original R9S several years ago. I had a chance to buy it back for a reasonable price (cheap enough I could make a profit on it).
It never ran 100% and I was too lazy to send it in. It would typically fail to chamber the #3 or #4 round out of the magazine using WW Silvertip, it wouldn’t feed WW 9mm “White Box” at all.
My youngest son latched on to it as soon as I walked in the door with it (it was the first pistol he had ever shot).
He took it to the range and it wouldn’t feed ANY round, he was trying Geco ball ammo and Federal HST 150 gr 9mm Micro. He was convinced it was a magazine spring issue. BUT it wouldn’t feed out of any of the three magazines I had.
Well being there are NO replacement magazine springs available he decided to try using a Kahr 6 round replacement magazine spring. He ordered a new Kahr spring from Wolff and when it arrived I looked at it and immediately thought “that’s way too long”! Well he was able to install it and fill the magazine to full capacity.
He installed it and went to the range, seven magazines later he had ZERO malfunctions!!!
This was using Geco 9mm and Federal 150 gr 9mm HST Micro ammo.
I can’t get over how simple (and cheap) of a “fix” this was.