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Thermold mag problem. Not feeding last round

callen3615

Sergeant
Full Member
Minuteman
Jan 27, 2010
90
12
35
Peidmont, NC
Hey guys, id appreciate some help on this one. I bought a few thermold mags for my ar15 online and they feed fine until the last round, I think the follower tilts the last round up so the bolt never contacts the back of the case. How do I fix this? Do I replace the followers? Has anyone seen a polymer mag doing this before?

BTW my ar is a dpms lower on a bcm m4 upper.

Thanks
 
Re: Thermold mag problem. Not feeding last round

I have neither seen nor personally experienced any such FTF with any of the Master Molder Thermolds that I have. They came equipped with anti-tilt followers when new so unless someone has monkied with your mags that shouldn't be a problem. The Thermold mags won't accept GI followers (or the Magpul anit-tilt units) and I am not sure where you can locate Thermold parts if you have one with a bad follower. Could also be a weak mag spring.

Out of curiosity, can you manually chamber the last round from the magazine? Also, when pulling back the CH on the last round, are you able to visualize a tilt of the last round in the mag? Finally, have you tried any other magazines in it to see if this is a problem across the board? Oh...what ammo?
 
Re: Thermold mag problem. Not feeding last round

Yes. I can load a few rounds, rack the handle over and over and it ejects all the rounds until it gets to the last one then it slides over it. and it does appear to be tilted.
 
Re: Thermold mag problem. Not feeding last round

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Re: Thermold mag problem. Not feeding last round

Some people used to call these mags "thermelts" as they would get hot and the feed lips would get soft and either melt or let the rounds volcano up out of the mag.

So.....With that in mind it looks like yours <span style="font-style: italic">may</span> have gotten hot enough to distort the magazines feed lips and they are not holding the round correctly on the last round.

Or... the spring is not holding enough tension on the follower to keep the round out of the center of the mag. It looks like in your pic the round is tilted twords the center of the mag. Causing the back of the round to tilt back. If you can try replacing the mag spring with a new one.

Try and duplicate this in another rifle also.

Just my .02
 
Re: Thermold mag problem. Not feeding last round

I have never shot a round through these mags. I have 3 and they all do the same thing. And I only have 1 ar.
 
Re: Thermold mag problem. Not feeding last round

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Ren</div><div class="ubbcode-body">Some people used to call these mags "thermelts" as they would get hot and the feed lips would get soft and either melt or let the rounds volcano up out of the mag.

So.....With that in mind it looks like yours <span style="font-style: italic">may</span> have gotten hot enough to distort the magazines feed lips and they are not holding the round correctly on the last round.

Or... the spring is not holding enough tension on the follower to keep the round out of the center of the mag. It looks like in your pic the round is tilted twords the center of the mag. Causing the back of the round to tilt back. If you can try replacing the mag spring with a new one.

Try and duplicate this in another rifle also.

Just my .02 </div></div>

Ah...I just love the Internet rumor mill!!
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Some Thermold mags were excellent while others were pure garbage. The original mags were designed and built by a US mfg in the 1980's. The Canadian military tested them and adopted them instead of going with the standard USGI mags. The Canadians bought a license for the tooling/molds for the mags, but instead of going with a proper polymer (I think it was Zytel sp?), they went with a different polymer and ended up with mags that were incredibly weak and prone to failure under full-auto and sustained fire. They ended up with cracked feed lips, mag bodies splitting at the seams and, ultimately, melting...thus the well-earned nickname "Thermelt" mags. That was only true however of the Canadian mags. Mags marked/molded with "MM" or "Master Molders" are GTG (they were made by the original US mfg).

To the OP...try disassembling the mag (or mags if it is more than one), clean them out, and inspect them. While you have them apart, look for any signs of "leftovers" from the molding process that may be interfering with the follower's operation or keeping it from fully pushing up toward the feed lips on the last round. Remove any debris/"leftovers" you find, lube em up and put them back together, and try them again.

Additionally, are the feedlips even/concentric in terms of the angle that they are holding the round in the mag or do they angle up from the back toward the front of the mag? I can't tell from your pics.

Finally...have you tried any other mags beside the Thermold mags in the rifle yet? PMAGs, USGI, other aftermarket mags, etc.? Any failures to feed or other issues with any other mags?
 
Re: Thermold mag problem. Not feeding last round

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: cpt. obvious</div><div class="ubbcode-body">I have never shot a round through these mags. I have 3 and they all do the same thing. And I only have 1 ar. </div></div>

Wait a minute...are you saying that you haven't actually fired a full mag using the mags in question yet?!?!

If so...get off the keyboard and hit the range, man!!
wink.gif
This is all academic/observational if you aren't sure if the problem will even occur under battery. Manually cycling rounds through a mag doesn't mean squat. If the mags work under live fire...then don't sweat how they work in the basement/garage/workshop...just shoot em.
 
Re: Thermold mag problem. Not feeding last round

Just saying what I know and tryin to help.
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Ive got a couple myself that I use as training, and lending mags.

Are you hitting the bolt release or riding the bolt home?

Good luck!
 
Re: Thermold mag problem. Not feeding last round

go shoot them,if they fck up trash them its a $4-5 mag,or remove the spring and stretch it and only use these mags for range use just my 02 cents
 
Re: Thermold mag problem. Not feeding last round

If the rounds dont go into battery when I manually cycle the bolt they wont magically go into battery when I fire them. I dont live near ranges and dont have many days off so Im lucky if I get to shoot once a month.
 
Re: Thermold mag problem. Not feeding last round

I stretched the spring in all 3 of my mags. They are about 50% on feeding the last round now. Im gonna grab a razor blade and go to town on the feedlips.
 
Re: Thermold mag problem. Not feeding last round

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: cpt. obvious</div><div class="ubbcode-body">I stretched the spring in all 3 of my mags. They are about 50% on feeding the last round now. Im gonna grab a razor blade and go to town on the feedlips. </div></div>


Be careful with that.
 
Re: Thermold mag problem. Not feeding last round

I had thermolds too and they seemed to work fine. However, if asked if I would trust them over P-Mags or Lancers...I would say no. A buddy of mine who does alot of 3 gun shooting and competition mentioned that the best mags are probably the regular GI mags with steel anti-tilt followers in them. I ran some of those during my tactical classes and I had no problem with jamming (unless having to manufacture one).
Being that there are many alternatives out there today...Retire the thermolds..or use them for range work. Problem with that, is that when your gun misfeeds off a bad magazine it really f%^^& you up mentally.