Blue Mags
Noun; The unsatisfied and disappointed feeling that arises when a trip to the shooting range ends abruptly due to unforseen circumstances before a single shot is fired. Similar to Blue Balls, but involving guns, not ejaculation.
"My buddy and I loaded up about 1000 rounds of ammo last night, and when we got to the range today, it was closed due to vandalism. Now we have a serious case of blue mags..."