I've heard people mentioning feed lips being spread out with magazine storage. Is that long term storage? I cycle my HD magazine once a week with another, it's a 30 round mag that I only load to 20. Is this going to mess up the feed lips?
I know for sure that happened a lot, early on in Vietnam with the 20-rounders. The modern aluminum 30 rounders are supposed to use a "reinforced" feed lip design, but they're still aluminum, and can still spread over a long period of time.
With Pmags, I wouldn't worry about it. Feed lip creep has yet to
actually happen, as far as I know. If you're using aluminum mags, keep the mag loaded with 28 rounds inserted in the gun, and feed lip spreading won't be an issue (the bolt carrier pushes the rounds down a little).
If you're using Pmags, keep them loaded with 30 and keep the impact covers on, and practice removing them. If you're using a carry handle, you can use that to pop them off really fast.
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Fast forward to today, extended storage is noted by Magpul to cause spread feed lips.
I think someone lied to you. I've heard that sort of thing a lot from the aluminum junkies, who claim the impact cover indicates a "design failure" or something. I guess you've talked to them, too.
Here's what Magpul and their representatives have had to say on the subject:
"Final answer, straight from the horse's mouth: the impact/dust cover is just a precaution. The PMAG polymers are very new, so we didn't have the luxury of 50+ years of material T&E like aluminum and steel magazine manufacturers. Are they necessary? I suppose that depends - if you're going to use your magazines as paperweights for the next 20 years, there really isn't any reason not to use the impact cover. If you're actually going to use your PMAGs as intended, the cover is probably overkill.
Personally, I have snap covers on my stockpiled mags, and no covers on the mags I shoot. Like I said before - we have some of the first prototypes sitting at the office, loaded with 30 rounds, no snap cover, and it's been almost 18 months. If your PMAG feedlips creep, send them back - I want to see it, because you'll be the first to report such a problem."
"Testing shows feed lip strength and creep resistance (deformation over time) are superior to those of other plastic magazines and USGI magazines. Various testing has shown minimal wear after firing tens of thousands of rounds."
"The PMAG™ was designed for long-term loaded storage with the impact cover in place. First, the impact cover prevents feed lip creep (when stored over 1 year). Second, the high-quality, heat-treated, stainless steel spring resists spring relaxation (weakening over time). Note: Spring relaxation occurs in all springs under prolonged loading. Spring design, material, quality of manufacture, magnitude of compression, temperature and many other variables can affect spring relaxation rates. Testing has shown the spring used in the PMAG™ does not experience detrimental levels of relaxation from prolonged compression."
"The impact cover locks into geometry on the front and back of the magazine exterior and presses down on the top round of the loaded stack. This redirects the pressure from the rounds that would normally deform plastic feed lips over time and cause magazine-related failures-to-feed."
People like to misinterpret that very last one, ignoring the earlier part that says Pmags are more resistant to feed lip creep than aluminum ones. Anything can bend if you apply enough force, and the impact cover really doesn't seem to be necessary. It's just a paranoid precaution.