280 GNR

So that means if you have a set of .358 Win. dies laying around, .375 H&H too, you can use them to start the neck down process. For fireforming you only need the shoulder pushed back far enough to chamber and a 7mm neck into the .280 chamber. Firing blows the rest out to fully form.

Sometimes you might get an uneven neck but that can be trimmed square. I get a split sometimes but that too can be trimmed out for use over several firings. For maximum case life just bump the shoulder back to chamber easily and size the neck to hold the bullet, no crimp needed. I chamfer only, to fit bullet into cases.

I look around for any other die sets I own that might be useful for necking down. A .44 Mag is basically .30-06 size so a .356 GNR would even help necking. Get creative and lube well. .338 Win. (if it reaches), .308, .30-06, 7mm Mag. & Mauser, etc. The more steps the less stress on the brass but it's not that critical. You have to get that neck in the chamber and the action closed on it. The rest will fill out.

A minor .280 split, brass temper related, fresh fireformed.