I just recieved my first Thermold 30 rnd mag.  Tried inserting with the bolt closed and it would not catch, falls out.  h
Also, releasing the mag with the bolt closed is a problem when using my Norgon Ambi release.

Any ideas?  

Thanks!

I have the same problem with my Thermold 30/45 round mags. When I insert them with the bolt open some will even prevent the bolt from closing. My suggestion is use USGI mags.

Insert with bolt open, drop bolt several times. It shaves the lips and then the mag will work fine.

The recommendation to use USGI is spot on, but everyone needs a Sunday Go To Meetin' Thermold for dress up. They are the most handsome of the AR mags.

Some Thermolds are not finished on the upper back surface where the finger of the bolt stop contacts the rear of the mag's follower.

Does your Thermold have a U shaped cutout there?

Now look at a USGI mag.  See the difference?  The bottom of the U cutout binds on the bolt stop.

Simply use a Dremel Tool (R) to fix it.

[quoteSimply use a Dremel Tool (R) to fix it.


That's like trying to refill a disposable butane Bic lighter!!!.

does'nt seem like like a waste of time to try and make an unreliable mag or one that does not fuction properly
work with a Dremel. the kind of tool that has screwed up more firearms and put food on the table of more gunsmiths then can be counted!!..

Toss it, pull out a ten and a five and replace it with a new mag.  Don't put Bald tires on a brand new car

In this case, SOME Thermolds are not finish trimmed in back.  There is a U shaped cut where the finger of the bolt stop contacts the rear of the mag follower.  The bolt stop bottoms out high in the bottom of the U and the mag won't seat.  With that area properly trimmed (compare to the rectangular cut of a USGI mag) the bolt stop will bottom out correctly and the mag will seat.  A Dremel is the tool to use here to turn a problem mag into a perfectly workable mag.

Pictures proved upon request.

The other problem, there is an angled rib on the Thermolds that contacts the beveled area of the mag well on bottom.  There was no requirement for any special angle on "mil-spec" receivers as the USGI mags don't have this rib, only the Thermolds, which are not US mil-spec.  Even the Canadians don't use them now.  So, this rib interferes with some receivers, and trimming it will fix that problem.

I don't take a Dremel and just grinding for no reason.  It is aways easy to remove material, but a real problem to put it back on later.  When I troubleshoot, I like to really spend time on getting to the bottom of the real problem.

The problem with my Thermolds was the feedlips contacting the bolt.