Loaded thermold mag Dec 1999. Shot it today.

[ride57]

As title says, I shot a thermold mag that I loaded Dec 1999. Ended up at the back of the safe, found it a couple years ago and decided to wait to 20 years to shoot it. Had to use the forward assist 7 or 8 times to get the first round to chamber. The rest fed just fine, no issues. The recoil spring is a Tubb flat wire spring that has maybe 100 rounds on it.


https://studio.youtube.com/video/VhECN-BnP-U/edit

[Eurodriver]

This is great.

What caused the issues with the first round?

[opngrnd]

Excellent info. Thanks for sharing.

[LewWallace]

It's good to have an account like this proving what it is so often said: it is the compression/de-compression of a spring that will wear it out, not keeping it compressed or decompressed. Proof is in the pudding, as they say. Kudos.

[Biggy]

Don’t like that first round failure to feed correctly though, Under the right circumstance, that could have been disastrous.

[ride57]

Not exactly sure on the first round. I was able to push the rounds down a bit before I started. I just tried a pmag loaded and it did the same thing, a gi mag worked fine, then the second gi mag hung up on the first round. tried other ARs multiple times (2, 1 aero precision and 1 anderson) with Tubb flat springs and they worked fine with different loaded mags ( I need a lulu).
The receiver in question is a bushmaster.

So, I think I have uncovered a issue with the bushmaster I have had for 25 years and never had this problem before, and it looks like a spring issue with the flat spring ( or tube?). I will put a regular spring in when I get a chance and see what happens.

even before this test I was a believer that just being compressed does not ruin a spring, but it is the cycles as someone pointed out above. ( if it was compression that ruined springs, every car on the planet with springs would very shortly look like a low rider)

[lordmorgul]

First round loaded at low speed without vibrations associated with gas driven bolt movement while others loaded at high speed. Gunsmiths will often say issues cycling by hand are not necessarily indicative of a problem with the gun firing normally. That’s why you have to actually go shoot it to see if the failure to feed continues rather than just hand cycling and then sending the gun in as defective.


Andrew - Lancaster, CA
NRA Life Member, CRPA member, Calguns.net contributor, CGF / SAF / FPC / CCRKBA / GOA / NAGR / NRA-ILA contributor, USCCA member - Support your defenders!

[Firefly]

I have some thermolds. Not at all my first choice but they work.

[ABNAK]

I have some thermolds. Not at all my first choice but they work.

I have a bunch of Israeli Orlite mags. Wonder how they'd fare?

OP, was going to say it didn't sound like a mag issue with the first round.

[Firefly]

I have a bunch of Israeli Orlite mags. Wonder how they'd fare?

OP, was going to say it didn't sound like a mag issue with the first round.

Poorly. Orlite is trash. I have one just because it looks weird. Never gets used.

Thermolds at the time were a great concept and provided they are North Carolina marked they are good to go usually.

Before Pmags, those and Eagle mags were the only polymer mags of note.

Like, if you have thermolds they make great trainer mags or screw arounds but I wouldn’t buy anymore