Rocky Mountain Cartridge
http://www.rockymountaincartridge.com/page7.html lists brass hulls in 24 gauge. I do not see what type of primer they use. Contact info is on
http://www.rockymountaincartridge.com/ .
Chamber inserts like Gauge Mate to let 28 gauge or .410 be fired could be made, if the chamber length is not a problem, or if 2.5" shells are available in those gauges. 24 and 28 gauge differ by about 0.030". If the chambers differ by about the same, that would make for a thin insert. A .410/24 insert would be thick enough to allow it to be made to extend into the 24 gauge bore. Then longer shells could be used w/o sticking in the insert.
