Original Colt AR 20 Round Mags - Rebuild kit?

massgun

massgun

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I admit my search skills stink, so I'm asking for info on sources for procuring rebuild kits for my Colt 20 Round AR mags. I have checked a few obvious places , but they are either discontinued (Brownells) or not in stock (a few other places). They work OK, but a couple don't consistently hold the bolt back on one of my AR's and I'm not sure if it is the bolt catch or the mag causing the failure (the mags are pretty old, no idea how many rounds thru them), so, if the kits are cheap enough, I wouldn't mind replacing them on the 5 or 6 Colt mags I have. Thanks.
 
mlaboss said:
The kits are just a spring, follower, and floorplate. Unless the floorplate is really messed up you probably don't need to replace it. For springs you can get them from Wolff: https://www.gunsprings.com/index.php?page=items&cID=2&mID=1&dID=79 (make sure you get the ones marked "For 20 round .223 magazines."). And followers can be had almost anywhere, e.g. Brownells: https://www.brownells.com/magazines...16-usgi-20rd-magazine-follower-prod71726.aspx
Click to expand...

Get Magpul anti tilt followers, they are the best out there and worth the cost of upgrade.
 
I used to have a website saved that had the spring, floor plate and aluminum follower but that computer died and I haven't been able to find it since, and the prices were reasonable. I have however found this site AR15 20 Round Spring & Aluminum Magazine Follower which has the spring and aluminum follower. From what I had read back in the day, the aluminum follower was the best one available for the straight body mags. So guys that had the 20 rnd mags with plastic followers were replacing them with the aluminum. Personally I don't notice the difference between the plastic or aluminum in my 20 rnd mags.
 
I use and like the Brownell's 20-rd rebuild kits. They usually don't take too long to re-stock and are worth the wait.

In the short term, try to better identify the cause of the mag failure.
~Take one known-good and correctly working magazine and strip it down, marking the parts as you go. (Permanent Marker works good)
~Now do the same with one of your bad ones, but don't mark them. (to differentiate between good/no good mags)
~Inspect each part against its counterpart. (body, follower, spring, floorplate)
Do you see anything grossly different? One spring shorter than the other? Rust? Feed-lips more open or closed between the two bodies?
Does the follower stop in the same position/height on both? Does the spring have an odd twist? How smoothly does the follower move in the body? Any stops or hang-ups?
~Now inspect the inside of the mag body. Rusty spot? Shiny rubbed spot(s)? Small dent or distorted body?

If you can't see anything obvious, take the entire "good" internals and swap into the bad body. Go to the range. Does it work?
No? = Body most likely bad. Try to repair and re-test, if fails again: Replace body.
Yes? = One of the internal components is bad, and is the best outcome because it is the easiest/most cost-effective repair to make and leaves you with a "fresh" correctly-working
magazine, after new internals are swapped in. You can also identify the culprit by swapping in know-good components until it functions correctly.
 
enbloc said:
I use and like the Brownell's 20-rd rebuild kits. They usually don't take too long to re-stock and are worth the wait.

In the short term, try to better identify the cause of the mag failure.
~Take one known-good and correctly working magazine and strip it down, marking the parts as you go. (Permanent Marker works good)
~Now do the same with one of your bad ones, but don't mark them. (to differentiate between good/no good mags)
~Inspect each part against its counterpart. (body, follower, spring, floorplate)
Do you see anything grossly different? One spring shorter than the other? Rust? Feed-lips more open or closed between the two bodies?
Does the follower stop in the same position/height on both? Does the spring have an odd twist? How smoothly does the follower move in the body? Any stops or hang-ups?
~Now inspect the inside of the mag body. Rusty spot? Shiny rubbed spot(s)? Small dent or distorted body?

If you can't see anything obvious, take the entire "good" internals and swap into the bad body. Go to the range. Does it work?
No? = Body most likely bad. Try to repair and re-test, if fails again: Replace body.
Yes? = One of the internal components is bad, and is the best outcome because it is the easiest/most cost-effective repair to make and leaves you with a "fresh" correctly-working
magazine, after new internals are swapped in. You can also identify the culprit by swapping in know-good components until it functions correctly.
Click to expand...

enbloc, thanks for the diagnostic tips. As for the Brownell's kits, they are the first place I checked, but their kits show as discontinued and no longer available.
 
I always go with the wild springs and antitilt followers.... not sure about 20/30rd compatibility....I wanna say it doesn’t matter or there was a simple solution...

Even easier is to just tweak the existing spring....
Usually just dissesembly and cleaning is enough...

Leaving mags loaded always takes a toll overtime.
 
That Fulton Armory Kit photo looks like it is for a 30, not a 20 round mag. (spring length, follower and especially floorplate which has no tab-slot for the USGI 20's)
Might just be a pasted photo though...

The photos attached are for reference only. They are for those who do not know the difference, as you most likely do, ~Matt

_DSC1415.JPG

20-rd internals:

(30-rd followers on left, 20-rd on right)
iu

(20-rd USGI mag springs usually have 9 full turns)
397848.jpg

(USGI 20-rd floorplates will have a spring-tab slot next to the ammo-tip release hole, which is smaller than the 30-rd, and on the opposite end. 20-rd commercial straight-body mags generally use a floorplate similar to a 30-rd mag.)
(Typical USGI 20-rd floorplate on left, 30-rd on right)
iu
iu
 
Last edited:
Enbloc, thanks for the reference pics. To be honest, I can't remember if I ever took an AR mag apart and I've had an AR since 1990. I also can't remember if I ever used a 30 round mag, except for an NES shoot maybe a few times, I usually shoot the AR's prone or from the bench where the 20 rounders work better. Now that I think about it, I can't remember a lot of things, must be getting old. [laugh]
 

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