MAGIC was the UMC new primed empty (NPE) that they sold as the equivalent of their ARROW shell loaded with bulk smokeless powder.
Back in The Golden Age, 100 to 140 years ago, there were lots of small loading outfits all over the country supplying shotgun shells to their local market.
Winchester head-stamped their NPEs 1901 --
while their factory loaded shells were head-stamped WINCHESTER.