View Full Version : PMAG 20s not extremely reliable?
I did some professional high speed camera testing yesterday. Some very interesting results on different things. I WISH WISH WISH I would have had an A5 to test, maybe next time.
I did test a Switchblock for RPM change. No surprises, it works very well to bring RPM down.
The biggest issue not related to other parts, was the the PMAG 20 failed a few times to bring the rounds up to a level the bolt would catch them. I would have bet you $20 the gun was short stroking, but nope. Clearly visible under highspeed is the bolt would go fully back, come forward, and miss the round completely and go on to close on an empty chamber. This happened on two PMAG 20s, and happened on two lowers. The PMAGs were probably a year old but didn't appear overly dirty, that said, I doubt they had been cleaned.
I had heard the PMAG20 was not as reliable as the 30, but this is the first time I had seen it happen and just by coincidence it was under high speed video.
Has anyone had similar issues with 20s? I really like the 20s, but I'm thinking I may have to pick up some steel or aluminum mags if this is a "thing" others have seen.
Did I just get some bad mags? How often do you guys clean your mags? At how many rounds does anyone expect dirty mag failure?
Canonshooter
04-13-12, 16:52
Yes. I have four of them, and one so far is NFG - same thing you're seeing. It happens with the last few rounds in the mag, except in my case the bolt catches the round forward of the rim, pushing it halfway out of the mag with the bolt slamming into the shoulder of the case.
I really prefer the lower profile of 20 round mags for certain uses, but have to stick with GI aluminum mags for critical use.
Yea, I should have mentioned that this was at max 5 rounds in the mag. It was full auto testing on an M16 lower, I would guess it happened between 3 and 2 rounds left in the mag.
I guess my issue was that without a highspeed camera... I would have only ever been able to speculate these mags were an issue.
I'm not bashing the PMAG20, and I'll continue to buy and use them as I haven't seen this in any of my ARs... But if I do, swapping the mag is now definitely very top of my list of things to try (as it should have been always, but I have had good luck with mags I guess).
Rifleman_04
04-13-12, 16:59
With my small sample size of three 20 round PMags, only one will lock the bolt to the rear after last round fired. I'm running an H3 buffer with standard carbine spring and carbine gas system.
None of mine have had failure to feed, though.
I have a few of them that I use in NMC courses. I don't use them at work though. I use them for the 8 rounds though. The bolt doesn't need to lock backs.
Dan
Wormydog1724
04-13-12, 21:54
I have five of the twenty rounders and sue them regularly. At least once a month during local 3 gun matches and I use one several times for hunting. I have never experienced any malfs of any kind. Several hundred rounds on each of them easily. I am shooting AR-15's, not M16's. They worked for me and I like the lower profile vs the 30 round mags, especially for hunting. (I know this isn't ihuntcoyotes.com)
Dionysusigma
04-13-12, 23:31
My sample size of one shows a less-than-stellar trend of not locking back on the last shot 60% of the time. FWIW, none of my setups use BAD levers (or related equipment).
An Undocumented Worker
04-14-12, 00:05
I've got 2 20 rnd pmags. Both have problems with bolt override if the mag is inserted on a closed bolt.
Insert the mag on a closed bolt and then try and charge the gun and the bolt just skips over the rounds. I noticed that the second round in the mag goes slightly cockeyed when inserted on a closed bolt.
My take is to use 30 rounders when reliability matters.
I have probably 6 of them. I use them for precision work, tapping steel etc. Ive never had a problem with them. Zero , zilch. And I have run many 5 round groups and I have stuffed them to the top, either way no issues. But I aint running full auto either:D
Maybe I'm lucky.
TangoSauce
04-14-12, 01:27
Similar issues as above on the last round in the mag.
Since I'm in CA I'm running 3 with ranger plates that have the 10 round limiter. 2 run great and one will about 20% of the time lock the bolt back. The others will lock the bolt back every time.
Interesting.
I know when I was firing my first 500 rounds out of my assembly, I did have 2 FTFeeds, same mag. Might have been one of the 20s (at the time I had 4 30s and 4 20s). I have not shot them since.
I will have to put them to task. Right now they are dedicated to my MK262 ammo, which I have yet to shoot.
I would like to see the high speed video. Would it be possible to post them?
I only use one 20 round PMAG and never have a problem with it feeding while shooting but now that this was brought up, I do remember that sometimes when I charge the weapon to begin shooting it does not feed the first round. Never gave it a second thought that it was the mag, always thought maybe I or my kids were maybe riding the charging handle forward.
Will have to keep an eye on it. I really like the 20 rounders and might have to pick up some aluminum ones to try out.
I would like to see the high speed video. Would it be possible to post them?
I'd like to, but can't. Aside from it not being my video, it was over an hour to transfer the raw data to an avi, so we just used it, got the data we needed and reset. It's pretty high end equipment and that seems to make everything a pain in the ass.
That said, there isn't much to see, gas streams out the carrier holes, it starts to roll back, goes full back, the rounds are sitting there in the mag, the bolt rolls forward, completely skips the top round on the mag, goes home. It's very hard to see, but it LOOKS like the follower is stuck tilted backwards slightly, the camera wasn't set up to see the mag exactly just the bolt, so who knows what was actually happening.
I will say, we had zero of this issue with 5 rounds loaded in the surefire 60. I'll be testing again in a month or two. I plan to test my new 20, an A5, maybe a PSA WAR receiver, and some other stuff.
Shame about the footage, but this is not the first time I've seen folks complain about the 20-round PMAGs here. Maybe it needs a new generation/model with an updated spring or something.
With the new 30-round model coming out, any word on an updated 20-rounder?
Dionysusigma
04-14-12, 13:04
I honestly kinda doubt it. There are several features of brand-new PMAG 20s that appear on Gen I 30s, which leads me to believe that their first iteration is sufficient for enough end-users to not justify re-engineering.
Just incase anyone was curious.... Fom the same day when the mags worked or we user usgi or a surefire 60
16" midlength, H buffer, m16 lower and Giessele select fire trigger, Noveske switchblock, AAC 556 can
Cyclic rates:
Unsuppressed SB-Normal: 850rpm
Suppressed SB-Suppressed: 925rpm
Suppressed SB-Normal: 1050rpm
Pumpkinheaver
04-14-12, 22:07
My 20 round Pmags have been flawless for the 2 years I've had them.
sinlessorrow
04-14-12, 23:09
good to know noodles and great info.
just so you know vuurwapenblog did a test of the A5 where they gave a 16" rifle a gas port of 1 making it very overgassed and the A5 showed no signs of bolt bounce while very overgassed.
good to know noodles and great info.
just so you know vuurwapenblog did a test of the A5 where they gave a 16" rifle a gas port of 1 making it very overgassed and the A5 showed no signs of bolt bounce while very overgassed.
Yea, saw that. But bolt bounce doesn't mean high or low cyclic rate. What's interesting is even at 1000-1100rpm, none of the guns tested had really any bolt bounce beyond a little jigger. Including a 10" upper. All using the same H buffer in the m16 lower. I saw surprised to see how little bounce there was with these configurations. The camera setup might not have been ideal (at 70,000 frames per second) but bolt bounce seems to be a complete non-issue this day.
I had mentioned problems with all (3) of my P-mag 20 in HK. Not chambering first round if inserted on closed bolt, failure to feed, failure to lock bolt back.
Because I use them only for zeroing and for competition that limits to 10 rounds loaded I decide to "upgrade" them. I installed 10rd limiters and USGI 30rd mag springs. They work flawless now. Without limiter they have capacity reduced to 17rd with new springs. I expect feed lips to fail sometime due to increased pressure on them.
Someone mentioned in another thread that FDE PMAGs seem to have more issues than the other colors. Is that a joke, urban legend, or true (some issue with that production run or something)?
bullittmcqueen
04-16-12, 10:37
I own three 20 rounders and have had feeding issues with all three. Same ones already mentioned, bolt not locking back on last round, not stripping round into chamber leaving chamber empty, and double feeds. I do not use them competing anymore, only if i'm doing prone work on steel in which the shorter length is useful.
I have a handful and luckily they have run just a good as the 30rds.
Meta-Prometheus
04-16-12, 21:20
I own two 20 round pmags and I can't say that I have ever had a problem with either. I've got about 200 rounds fired through each of them and I can't recall any malfunctions.
Have 10 of the 20 round PMAGS. over 3k through them. All have been perfect, never a problem with any of them.
One of my pmag20s has a mishapen spine and makes sending the bolt forward difficult even when loaded
One of my pmag20s has a mishapen spine and makes sending the bolt forward difficult even when loaded
Is that why that happens? Dam, i have a 30rd PMAG that does that but didnt know why, thank you for the info.
gunfighter48
04-17-12, 01:02
I've got 10 of the 20s and so far no problems of any type thru 1500 rds. The last time I had an AR was almost 16 years ago and I used USGI mags. I was always having to do something to keep them running. Don't have to do anything to my Pmags!! I've also got 10 30s and they have run without any problems also. I load all of my mags to full capacity and they still work great.
It may be worth messaging failure2stop on this subject. He mentioned in another thread his go-to HD weapon is an ar with a 20rd pmag and another 20 rd pmag in a redi-mag. He doesn't strike me as the type to choose a mag that has reliability issues.
I have a FDE PMAG 20 and haven't had a single problem with it. Guess i'm one the few lucky ones. I bought it a few months ago and haven't shot it that much but have put a few hundred rounds through it. I bought it for the purpose of using it as a hunting mag and hope i don't have any of these problems while i'm in the field.
While my 4 PMAG20's have run flawlessly, they're only there for bench days at the range or varmint huntin' - not for serious use.
Follower tension and mold material being the biggest things I've noticed being different, other than the obvious appearance differences.
SilverTongueDevil
04-17-12, 20:22
My 20 round pmags have functioned flawlessly even with steel.
I basically put away my 30round pmags *loaded* with my old GI ones *unloaded*...
Breadstick
04-17-12, 20:31
Both 20round Pmags I have were almost tossed in the trash. Heck my C Products 20 rounders (2) were smoother, more reliable.
I dismantled one Pmag 20 rounder, reassambled it, works great now:confused:. Havn't gotten around to the other Pmag though.
My old Colt 20 rounders (4) get used more than any other mag I have, and have been most reliable.
I bought (5) 20 rd pmags last month because I love the 30 rounders and have never had any problems with the 30 rds ones. Well, after 4 trips to the range with the 20 rds pmags and nothing but problems I started doing some reading about them. I wish I would have done this before I bought them. Seems to be several threads just on here about people having problems with them.
My gun runs 100% with the 30 rd pmags but I want the 20rds ones because I can use them prone and on the bench. I used all five of the 20 rds pmags in my Colt, BCM and Noveske and all three guns have problems running these mags.
With the 20 rds ones, the bolt fails to lock back 90% of the time. It will not feed the first round 50%-75%. And about 10%-20% of the time I have a jam where the bolt tries to feed the round in the middle of the case, bending the brass case.
It doesnt matter if I only load the mag with 3 rds, or 20rds, I still have problems.
Is there a solution to fix this problem?
Any other short 20 rd mags that run 100% of the time?
here r some pics of how the bullet tilts when the bolt tries to feed it into the chamber and the bolt bends the brass casing.
Did you do this, first?
http://store.magpul.com/contact
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