My magazines FTL on last round

[Handgun Midas]

It wasn't the ammo, it wasn't the gun, it wasn't me.
It was these two mags.

Took my Ruger P345 to the range today, for the first time in around two months, to fire up the JHP's I'd been hauling around in it for about four months. With both mags, 4 out of 5 times, the last round would not feed fully and jammed up the gun. This happened with the JHPs that I had, and a box of WWB FMJ that I brought along.

So I bought a new mag at the range, $40 for troubleshooting, which had no problems at all. I kept testing it over and over, but the new mag never failed on the last round whle the older mags continued to have problems.


So what happened? I kept these mags either fully loaded or empty for months, sometimes unloading one for some snap cap practice and then loading the JHPs back up when I was done. The mags have been dissassembled, cleaned, oiled several times.

Should I let them sit empty for a while? Stretch the springs a little?
Any ideas?

 

[The Lone Haranguer]

Failure to feed only the last round suggests a weakened spring (which stretching will not compensate for, at least in the long term), but I wouldn't have expected this so soon with a newer gun.

 

[Handgun Midas]

I'm letting the springs breathe today. I should get to test the mags out again tommorrow. Maybe try and switch the springs out with the new mag just to be sure.

If that doesn't work, I'll send the mags back to Ruger for replacement one at a time.

 

[JDGray]

Ruger has a plastic follower, but reduces capacity to 7, that supposed to be the fix. The double lip steel follower causes problems, if it hangs up.

 

[Handgun Midas]

Range time yesterday: the new mag was FTL-ing on the 8th round just as much as the other two. Left a message with Ruger about it, gonna try and get plastic followers or some new mags from them. Barring that, I have to look for metal followers in other mags that will work properly and give me full 8rd capacity.

Funny thing is, why is this BS just now cropping up now, 500+ rds through the gun and at the end of any reasonable break-in period?

 

[JDGray]

My friends P345 was doing the same thing, and I polished the breech face, and shell notch on the left side of breech face with some 800 grit, on a popsickle stick, and worked up to 1200. Its easy to remove the extractor, this maks the job easier, and wedge some paper under the loaded chamber indicator.

 

[Handgun Midas]

I polished the feed ramp up to 2000 when I had the thing apart yesterday.

Talked to a guy at Ruger, who comes reccomended by the Ruger forum, and he claimed the issue was with a "casting mark" left in the slide, and not the mags.

He offered to repair it for me, and I opted to send him pics of the slide to see if this suddenly obstructing mark is in fact in the slide; and then we'll go from there.
Not having to modify or replace my $40 mags would be big plus.