G'day John,
these cases could be used to make 450/400 3 1/4, but the rim would most likely need to be thinned down. This cartridge I believe uses the 450 3 1/4" as its parent case, which has a rim approx. .040" thick. These cases have a rim .065" thick.
I had a double 450-400 3" once that had one of its rim recesses cut slightly too deep, and when loaded if you tipped the rifle up and down, you could hear the shell moving. I had to make very thin washer that I slipped over the shell on loading, which took up this slack. Once I'd fired all the brass once this way, I reloaded the cases as if they rimmless, headspacing off the shoulder. This also showed me that the rim recess was cut seperate to the chamber, because after the cases were reloaded in this way, any case headspaced perfect in either barrel.

Moral of my story; if your 450-400 3 1/4" works perfect with the correct thin rim, these will work but need to be modified. If the rim recesses are a little deep, these will still need to be modified, but give you the chance to custom fit them to a given rifle and remove any headspacing problem that may exist.

These cases can be used to form the following [ list enclosed with cases ] ; 333 rimmed Jeffery, 360 No 2, 369 Purdey, 450-400 BP, 450-400 3", 450-400 3 1/4", 450 N.E 3 1/4", 11mm Murata, 11.15mm Werndl M/77, 11mm Gras, 12.11mm Norway & Sweden, 7x66mm VonHofe, 9.5x73mm, 10.25x69R mm, 10.3x60R Swiss, 40-110 Winchester Express and 50 Maynard 1865.

Hope this is of some help,

Ron.