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Old 07-02-2013, 13:54   #1
imaguy3
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7rd GI mag dimension/failure question

Hey all, I recently bought my first 1911, a Sig Carry Nightmare. A coworker gave me 2 G.I. style mags to go along with the two that came with the gun.

I was testing all the mags and found a problem with one of the GI style mags and had a question. Of the two mags that were given to me, one is a Colt mag, and the other is an unknown brand. During testing the Colt mag was not locking the slide to the rear, but my other 3 mags all worked fine.

Upon closer inspection I found the follower of the Colt mag was going up and over the slide lock lever. To troubleshoot I swapped the internals (both mags had the same spring/follower) from the unknown mag (which worked fine) into the Colt magazine tube, and swapped the Colt internals into the unknown tube.

Again the Colt mag tube still wasn't working, but the unknown was... which means to me the only variable left is the magazine tube.

I broke out the calipers and measured the gap on the front edge of the feed lips, right behind where the slide stop is, on all mags, below are my results..

Colt: .497"
unknown: .470"
Sig mags: .475"

My thought is the Colt mag is out of spec and allowing the follower to move around the slide stop, however I can't find specs anywhere on the magazine feed lip gap.

Can someone confirm/deny my suspicions? Likewise is it possible to save the mag or is it trash?

Last edited by imaguy3; 07-02-2013 at 13:56..
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Old 07-02-2013, 14:02   #2
faawrenchbndr
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I've yet to see one revived once the feed lips were spread.
You can bend it back, but it will spread again.
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Old 07-02-2013, 16:08   #3
imaguy3
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Quote:
Originally Posted by faawrenchbndr View Post
I've yet to see one revived once the feed lips were spread.
You can bend it back, but it will spread again.
yeah that's what I thought... but is that definitely my problem? I can't seem to find the specs on what the feed lips should measure...
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Old 07-02-2013, 18:11   #4
Jason D
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You can buy the tool to reform the magazine feed lips from Brownells.
However I too have never seen one that has spread work like it did as new.

Since the magazine was a gift, you wouldn't be out anything to give it a few tweaks. I would use a pair of pliers with the jaws covered though, instead of investing in the tool. If I had a lot of magazines to work on I would get the tool though.
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Old 07-03-2013, 11:03   #5
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It seems like the time and effort with possible monetary investment into fixing this "Colt" mag is better spent buying a brand new mag and just chuck the Colt mag in the garbage bin.

Or put some big ass Red X on the magazine sides and relegate it for malfunction drill practice.
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Old 07-03-2013, 11:13   #6
faawrenchbndr
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Quote:
Originally Posted by imaguy3 View Post

Colt: .497"
unknown: .470"
Sig mags: .475"

My thought is the Colt mag is out of spec and allowing the follower to move around the slide stop, however I can't find specs anywhere on the magazine feed lip gap.

Can someone confirm/deny my suspicions? Likewise is it possible to save the mag or is it trash?
I just measured three mags that operate perfectly in a few Colts and a Springfield.

Metalform: .4755"
Colt: .4685"
McCormick: .4940"
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Old 07-03-2013, 15:29   #7
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Magazines labelled "Colt" are not made by Colt's. They are some of the least consistent of available magazines in my experience.

Get Chips or Tripps. Accept no substitutes.

It always amazes me how many comments and questions float around on the web that have as their root problem lousy magazines.

A good 1911 will run all day on good magazines. It won't fire seven, consistent rounds with a lousy one.

Again, magazines marked "Colt" are among the worst available.

You can put a Tripp Kit in the magazine bodies you have and they'll work a lot better (probably). But, that would be lipstick on a pig, in my opinion. Magazines are easily bent in competition and serious practice. Good ones are less likely to get damaged from "normal" use (i.e. Tripps).

p.s. See Kuhnhausen for a description of various magazine lip configurations. Different measurements at the front don't mean much. The critical dimension is the point at which the magazine releases the casehead. That point is way back from the front. This release point is different for different configurations (again, see Kuhnhausen for a thorough explanation).
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Last edited by Three-Five-Seven; 07-03-2013 at 15:35..
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Old 07-03-2013, 17:57   #8
Jason D
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The Colt factory magazines that came with my S70 Gold Cup are the GI type and made by Metalform. Both magazines are good to go. Then again I have always been happy with any Metalform magazines I have purchased.

I have read that the new Colt magazines are made by Checkmate. I have a bunch of those, and they do seem spotty. They are marked Kimber though for what it's worth.
Seems to run about one bad mag out of three.
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Old 07-03-2013, 18:48   #9
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I've used Wilson, Tripp and CMC. The Tripps are my favorite but the CMC's are the best value out there. If your gun is in spec it should run any of these magazines without fail. I used to try to salvage and rebuild but mags by design are expendable and should be replaced when signs of damage or fatigue are evident. I mark and number mags for every gun and if I have more than a few malfunctions with the same mag it may be marked "Range Only" or smashed with a hammer and left in a garbage can.

You get what you pay for and a free mag that don't work is just trash, I wouldn't even invest in a rebuild kit for one, let alone try bending the feed lips. If it was my own mag since new I may put a new spring in but for the price of CMC mags I usually don't bother.

One thing to remember is that you don't want the rounds jumping out too early and forcing the extractor over the rim.
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Last edited by MStarmer; 07-03-2013 at 18:50..
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Old 07-04-2013, 10:51   #10
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Also, there are counterfeit magazines, not made by or for Colt.
Not worth spending money on. Tinker with it and see if you can get it good enough for practice and mark it not to go to war with.
I have a worn out mag that can no longer be tweaked into action. I marked it and use it for the Barney Bullet at IDPA.
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