Ruger 40 S&W auto-unloader?

[376Steyr]

So I'm at the range with my new Ruger SR40, using the two magazines that came with it, working up a load with Blue Dot and the NOE 200 gr. flat point. Suddenly, I notice that occassionly a loaded round will jump out of the gun and land on the bench. Even stranger is the next round in the magazine would already chamber and fire normally. This seemed to happen only with the second-to-last round in the magazine. I have found many ways to make autoloaders jam over the years, but this is a new one on me.

I was casually alternating shot strings between two apparently identical magazines. I was running low on ammo when I noticed the problem, but I might have isolated it to one magazine. I'll properly mark the magazines and shoot some more, paying close attention to function this time. I'll also chronograph the load to make sure I'm not pushing the gun into some insane recoil impulse it was never meant to handle.

Anybody else have this sort of thing happen to them? Rounds flying free and the gun just goes ahead and loads the next one after the ejected round?

[KYCaster]

Weak magazine spring.

The spring is too weak to hold the round in the mag under recoil. The round pops out when the slide hits full rear travel then the next round is fed into position before the slide starts to return.

Clean the mag and replace the spring.

Jerry

[376Steyr]

That does make sense. I was staring at the magazine feed lips, trying to discern some differences between the two magazines, and couldn't see any. Thanks!
Weak magazine spring.

The spring is too weak to hold the round in the mag under recoil. The round pops out when the slide hits full rear travel then the next round is fed into position before the slide starts to return.

Clean the mag and replace the spring.

Jerry