I agree w/ Ted that a 24 bore probably will never approach the value of a 20 bore unless you find a 24 bore drilling. I've read of a Neumann 24 bore grouse gun, if memory serves me correct. The 24 bore was for shooting songbirds("Four and twenty blackbirds baked in a pie, ..." or something of the kind - kids chant) along w/ the 32 bore which was more of a specimen/garden gun exported to South America. I think Iver Johnson & H&R made of 24 bore of some sort. From time to time I pick up a box of 24 or 32 bore shot cartridges and Midway carries 24 bore Fiocchi, the only game in town:
https://www.midwayusa.com/esearch.exe/search?search_keywords=24+gauge&category_selector=653 .
Kind Regards,
Raimey
rse