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Posted: 2/16/2016 5:12:48 PM EDT
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Lifetime lurker, finally the search and Google has failed me, so I must ask my own question.
I have some Colt 20 rd 5.56 straight aluminum magazines. They will not lock the bolt back on the last shot, this has been consistent with good ammo (Hornady, Federal) and cheap ammo (Prvi, Wolf Gold). The magazines were made in 2012, and have the black plastic follower. I have tried running them at capacity, and downloaded to 18 rds, still not locking the bolt open. My rifle is a 14.5" mid-lenght upper, Fail Zero AR15 carrier, carbine buffer and carbine spring. Standard lower, normal unmodified bolt catch. I have had zero problems with USGI 30's, Lancer 20 and 30s, PMags of all kinds, including 1st Gen 20s. If I didn't live in Hickenpooper land  I'd just toss or sell them, but I'd really like to find a way to fix them, seeing as I can't get any more.
Anyone have any ideas or solutions? |
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Try a NEW SPRING in one. See if that helps.
I'm kind of surprised. I own more straight 20s than anything else, and have never had a problem with any of them. |
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Insert empty mag and manually retract the bolt. Does it lock open?
That is your first check. If it does not. Then you need to check the follower and hold open. Does it do this with multiple different mag's? You might be under gassed or something is keeping the bolt carrier from moving far enough to to the rear. From your description it doesn't seem to be an issue with other mags so this would point to these mag's binding the bolt catch some how or the followers not engaging the bolt catch well enough to move it up to lock. Maybe try swapping one of the followers from a mag that works into one or more of these. If that solves the problem, figure out what the difference is in the followers or jus t replace them with new Magpul ones. They are cheap! |
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Essayons and KILLERB6, that's why I'm a little baffled, the straight 20 is supposed to be excellent. I had an old one (should have never sold it) that had the metal follower, it ran great.
I just tried inserting the empty mags and retracting the bolt, locked open every time, tried it three times with each magazine. I may try the new springs, Brownells has them for $5 each. Maybe whoever makes them for Colt (Okay I think) hosed up the springs. The Magpul follower doesn't work in a straight 20 from what I understand, the rear of the follower needs to tilt down to allow for the angle of the cases as they stack against each other. I do have their followers in all of curved 20s and all but two of my 30s, no issues. Just discovered someone is still making the aluminum follower, maybe I will try to get my hands on a few and test them out. |
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Yup, you need a tilt follower. In addition to the spring Brownell's sells a complete 'rebuild' kit with spring, follower and I think a new baseplate.
But I think that kit is about 9 bucks, and they always put those straight GI 20s on sale for 10 bucks. If these mags are only three or four years old I'd be surprised those springs are wore out. |
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Quoted:
Insert empty mag and manually retract the bolt. Does it lock open? That is your first check. If it does not. Then you need to check the follower and hold open. Does it do this with multiple different mag's? You might be under gassed or something is keeping the bolt carrier from moving far enough to to the rear. From your description it doesn't seem to be an issue with other mags so this would point to these mag's binding the bolt catch some how or the followers not engaging the bolt catch well enough to move it up to lock. Maybe try swapping one of the followers from a mag that works into one or more of these. If that solves the problem, figure out what the difference is in the followers or jus t replace them with new Magpul ones. They are cheap! Don't do that. A thirty round follower will not fix anything in a 20 round straight magazine but will make things worse. If anything is wrong with a 20 round straight mag it is the spring. The followers and floor plates don't wear out. |
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Double check that the springs are fastened to the follower correctly.
And see if any flashing is present that is preventing the follower from rising to full height and tripping the bolt catch. Might be fixed with a knife or sandpaper. My 20's have alloy followers and I'm assuming the plastic ones are of the same shape. |
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