Any ideas why that should be so, Sam?
Probably multifactorial. It gets discussed on both the skeet and reloading SGW subforums. For decades NSSA skeeters have written there, and elsewhere, about it. The HS hull's been around some time now, but prior to it's appearance most wrote adamantly about superiority of the STS factory loads. Guys from our club who had lessons said they were told to use factory STS-only in .410 competition.
I didn't form an opinion until started shooting NSCA. My reloads w/Win Magnum #9 in CF AAs worked well enough on a skeet field. But they're not in the same galaxy with STS or Super Sports when pushed to 35 yds or more.
You're right about the payload. The 205 gr drop comes from one I hogged out some. Should do more surgery, I suppose. The unmolested 1/2 oz 502 throws about 185 gr with Win #9. Much closer to 1/2 oz with Eagle but that stuff is pretty soft. In 12s need to choke up to get equivalent breaks vs West Coast or Lawrence.
Then there's hulls vs payload. NSSA rules allow a certain % over on payload, so you could push the shot charge beyond 1/2 oz. Bill Murphy has written about this here, not sure what hull he was using. NSCA does not allow the same "deal", and getting even the full 1/2 oz into a CF hull has frustrated me.
NSCA game pushes #9 shot size. A practical consideration is unreliable 1/2 oz shot drops from a 9000 with anything larger than #9 - bridging and messes.
I agree concerning "budget" .410 ammo. We've seen Estates come apart at base on first firing. Not something I want with a Model 42.
