With respect to shooters within CONUS:

That you can walk into your average gun store and find on the shelf - none.

That you can order easily from numerous sources and expect to reliably find it in stock - .470 and 9.3X74R.

That you can order from fewer sources and with possible stock-out aggravation - pretty much all of them.

Were I shopping for another double rifle, I wouldn't hesitate to buy, or order if I was having one built, a .375 Flanged Magnum, .360 No. 2, .476 Westley Richards, etc., because I simply can't see availability of factory ammunition as even the tiniest of issues. I've hunted with double rifles for years and, as birds of a feather flock together, I know a lot of other guys that do so as well. Other than to buy one or two five-round packets out of curiousity or for a laugh, none of the guys I know actually use the stuff, especially in the field. While a lot of factory ammo is used in the field in bolt rifles, I would think very little is used in doubles - handloads are the norm.
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