After you receive your new mags, dis-assemble them one at a time, and clean them thoroughly with alcohol.  At this point, once you have thoroughly de-oiled the mag bodies, I suggest you paint them, inside and out, with Brownell's AlumaHyde II paint in a color of your choice.  Why?  Because new Parkerizing, thoroughly de-greased is an almost perfect paintable surface, and the AL II epoxy paint will rustproof your mags until 10 years from now when the springs wear through both the paint and underlying Parkerizing.  I've done this, and it works.

If you don't want to do the above, then since the mags  are probably parkerized, then coat the inside and outside of the mag body with a thin film of lubricant.  Do the same to the follower and most especially the spring.   If any parts are blued, as opposed to parkerized, apply a good coat of auto WAX, not polish.  This will keep the blueing from rusting, but you will need to renew the wax every so often, depending on usage.

If you have older mags, take measurements of the new springs while you have the new mags dis-assembled.  Your old mag springs should not be more than two coils shorter than the new springs.  If so, replace them, and order some extra springs for the future, if you happen upon some mags that simply need new springs to make them work.  Mag springs with rust pitting should either be relegated to range use, or discarded.  Discoloration remaining after removal of surface rust is tolerable, but pitting, unless very minor, as in a few tiny spots, is problematic.  Range use only, and buy the replacement springs before Hillary gets elected, heaven forbid.  

Mag springs, and followers are wear components, although most folks don't think of them as such, but they should.  both of these components wear out with use.

Concur with advice to buy CMI mags from 44mag.com, as they are also GI-issue, and currently as good as it gets; Fully on par with the best of the NIW GI mags, seldom seen nowadays.  I've done so myself, FWIW.

Thank you for the positive comment.  We have disagreed in the past on certain technical points, but we have never said that either of us was ignorant, or was technically ill-informed.

I consider you an expert on some things M-14/M1A related, but there are some things in which we dffer, as friends.

Here's the deal.

Unless the Genuine, USGI mags are New-In-Wrapper (NIW), they are suspect--and I would personally inspect any NIW mag I intended to use prior to use.  I understand about collectibles, and that is another consideration.  Take the mags apart, and clean/inspect them internally.  Put a thin film of oil on the springs, follower, and on the inside of the mag body.  You will need to repeat this fairly often, depending on use..  If you see anything but a very slight, surface rusting on the mag spring, then plan to replace the spring.  Any rust pitting on the mag springs is cause for instant replacement.  You MUST buy some NEW mag springs from a known, GTG vendor.  Compare your used mag springs with the new ones for length.  ANY old mag springs shorter than TWO coils of the new mag springs must be replaced.

Now, I understand that my recommendations above might seem a little bit much.

Not so much if you depend on every singe mag you own to save your life.  Magazines are the most fragile part of most semi-auto firearms.  Have plenty, and make sure all of them are GTG.  Your life might depend on it.

Boeshield's good stuff, for the right application.  Epoxy paint over fresh, well-prepared park is hard to beat, though.  YMMV.

For those who don't know, Different is widely acknowledged as THE M-14 Guru.

More to the point: he is an author of a number of widely-read articles, and a number of acclaimed books about the M-14.  When Different talks about the M-14, I shut up and listen.  YMMV.