Originally Posted by TactiCool
The only reason GI mags were ever loaded to just 28 rounds was so that it would more easily seat on a closed bolt. It won't compromise function at all to load them to capacity, even for long-term storage.
I won't disagree with you. I'm simply saying that for several years that wasn't what was being taught in the Colt AR15/M16 armorer classes for LE users.
For a while we were told that Colt was cycling out its function testing AR mags something like every 90 days (due to wear). Dunno if they're still doing it that way.
I can say that I've seen surprising service exhibited by AR 30-rd mags (as sold by Colt and a couple other companies who sell to LE/Gov buyers), even when they're being used for a few years (constantly being loaded for training/quals). Once it may reach a point where occasional (as necessary) cleaning, and maybe a follower or spring replacement, can't keep them running, though, they're ready for destruction/discard and replacement. I'd be more careful of service use mags, though.
And as for every magazine spring ever made being properly designed for the box magazine in which it's going to be used, and being tempered with exacting precision?
Well, cost savings on materials & manufacturing, meeting low bids and/or the use of third party vendor supplied parts may not always allow those lofty ideals to be realized.
That's why I've long since stopped being surprised, amazed, disappointed or annoyed when an occasional spring (or set of springs) fails to provide similar length of proper service as some other spring (or springs), even when it hasn't been subjected to numerous compression cycles, but only being left fully compressed.
People will continue to debate this subject as long as we're using wire coil springs. I doubt everyone will ever reach complete agreement.
I'll continue to remain unsurprised when 9mm mag (and recoil) spring service life may sometimes seem to exceed that of .40/.45/.357 pistols, too.