What percent of capacity can you load and how long can you keep it loaded before the magazine spring begins to "remember" the compression it's under and begins to weaken?

Back in the 70s used to have a lot of problems with pre-loaded M16 magazines. Don't know if it's the real cause or not but we used to blame misfeeds and jams on springs weakened because the magazines were filled to capacity.

Opinions/findings differ on this subject. I've seen people say you should rotate loaded mags so the springs can rest, and I've seen people who say it doesn't make any difference. I try to rotate mags at least every couple of months in the few I keep stacked full. Not saying that makes any difference what so ever, it's just what I do.

I've also seen people advocate to leave one round out of M16/AR mags to avoid feeding problems. Never seen it make a difference, but never had feeding issues I could attribute to a mag being plumb full either.

Springs to not wear because of constant tension, they wear by use -- being stretched and compressed multiple times. Leave your mags loaded, it doesn't hurt them if they're well manufactured.

Bside is right... Springs don't wear from being compressed. It's the actual action of compression and release that wears them.

Not an opinion; just physical fact.

+1 and if you do have a spring issue or just have an extra cubby or two in the parts bin there is always: http://www.brownells.com/search/index.htm?k=magazine+springs&ksubmit=y&f_a=49