My father-in-law's son shoots 577/450 in a BSA Martini-Henry and scarfed up a set of 480 Ruger dies from me to neck 28 ga. brass shotshell hulls that he gets from Graf & Sons. He uses these to build his cartridges.

28 ga? Why am I thinking it's the 24 ga that would fit? I should check (or you might do it? ) but in my opinion the 24 ga can be shot in the .577 Snider (which is the parent of your 577/450?)

I believe 1 works better than the other....the rim will fit without trouble,and the other will need poked back out if my memory serves me right.

Everything I've seen so far says use 24 gauge brass shells to convert to .577/450. I've got some on my Midway wish list, but they are out of stock.

Still haven't shot them...

The Brass I use in the Snider is Magtec 28ga not 24ga. The 24ga needs to be reshaped in a press but the case rims are wide enough to work in the Snider extractor. The 28ga on the other hand fits the Snider chamber and fire forms on first shooting, just need to knock out the fired brass with the Sniders cleaning rod.
The cases after firing a few times get a bit lose on holding the ball so I just dry patch them when pressing them in the case in a bench vice.
Haven`t had any leading issues that I have noticed and the barrel is pristine apart from one pit ..(cave) halfway down the barrel. Powder charge would be around 50gr FF so not pushing the ball hard, its an old gun , prefer it goes bang rather than Boom.




copied and pasted from another site....the author knows his stuff.

Ya'll may be right on the gauge correction to my post.
I haven't personally been involved in the conversion and only through conversation was it outlined to me.
I do know that .480 Ruger dies were used as he bought them from me.
Anyway, I hope the needed reloads are able to be constructed.
Good shooting fellas!
Thanks,
Jimmy