I know, I know. It hurts to let an expensive magazine from your expensive gun hit the dirt. Dirt! Ug! Tiny particles that can seriously screw up your gun. (A Kimber!) And what if you damage the magazine? Your LIFE might depend on that mag! Sorry Mr. OCD, but if you have any intention of ever using your gun for self-defense (i.e. reloading on the fly), you need to let it go. Literally. To quote Mr. Dogg, drop it like its hot. Well, first . . .
Check to make sure you have another magazine with bullets in it. ‘Cause if you don’t, and you still have some bullets in the “old” magazine, you might want to belay that re-order. And if you don’t have any bullets in the old magazine, and you don’t have any in the “new” magazine it’s time to run like hell.
In any case, train as you mean to fight. Label practice mags. Drop ’em. Straight down. Into the dirt. Eyes on the target. Gun facing target. Insert new mag. Reassess. Resume fire as needed. Or not.
If your dirty magazines eventually malfunction, even better! You’ll know what to do when things don’t go as planned. Which they never do.
When you’re done training, clean your gun, blast some air though the “dirty” practice magazines, load up your pristine magazines with hollow points, insert one into your gun and spend the time between this training session and the next one avoiding trouble.
That is all.
I consistently drop empty/half-empty (and occasionally full magazines on accident) into the sandy, gritty, mini-pebble laced dirt at Rio Salado Sportsman's Club during the Tuesday Night Steel Matches. Sure, they get dirty and aren't pretty when I get them home, but I can clean all 5 magazines in less than 10 minutes. Take them apart, wipe/rinse/spray them clean as necessary, use a mag brush and make a couple quick passes, wipe down with a dry, clean cloth, and reassemble. As RF puts it, it's best to practice like you mean it!