Regarding my thoughts on rechambering a 375 Winchester 94 to take the 356 Win case, my buddy has a 308 Win reamer but has steepened the shoulder to make the neck longer.

Could that reamer be taken in farther to at least allow 356 cases to chamber and possibly more to increase powder space?

What might a die maker charge to match that chambering?

I realise that cartridge might then have a slight bow near the head. Would it matter? Has anyone ever made such a cartridge before?

Sam You are going to pay plenty for a custom set of dies. I would suggest going to a 375/444 AI. I had a TC Encore barrel rechambered and CH4D had a set of dies in stock for that calibre. Not sure if your action will handle that cartridge length

Consider that when you run a reamer in deeper, you are no only extending the length, but are also increasing the OD of the chamber; it all being a taper, on tapered cases, and depending on how much taper there is. Which on a 308, it tapers from .473 to .453. The case that is, and of course, the chamber is larger.
But you aren't going to run it in much deeper.
Go for it.
Custom dies; half what the rifle cost. Only for rich people. Not me.

Thanks snowman and dpcd,
Maybe I should ask JFE where he got the 308W reamer for his conversion. Would dies for that wildcat be any cheaper/easier to find?

I ran a 308 reamer in an extra 6mm to make a 7.62 by 57. The base wasn't enough larger to be a concern.

S338 - my conversion used a regular 308 reamer. Most gunsmiths that do rebarrel/rechamber work will likely have one. Sticking to the standard 308 reamer made finding 375/308 dies relatively easy. I bought Redding dies as they listed them at the time and you could likely get Simplex locally to make a set. Your toolmaker mate could probably modify a set of Lee 308 dies to suit, as their dies are not that hard. Your 375 Win seating and crimp dies might work too. I know Lee’s FCD for the 375 Win works on the 375/08 shell.

Jim Kent in Toowoomba did my conversion and he’s now done a few unusual conversions for me. A lot of smiths just don’t like working on anything other than bolt actions.

The 308 case is already an improved design IMO and any capacity gains by improving it further are not worth chasing, again IMO.

I do know a smith that has a 375/444 reamer in Oz, but without major alterations I doubt this length shell can be accommodated in the Win 94 action, unless you simply restrict the cartridge OAL to 2.55”.

Thanks Bill and Joe,
so, I guess that idea could happen but probably won't. I'll ask about those 308W reamers.

I've been reading my mate's book BIG BORE Rifles and Cartridges and take it the 375/444 mentioned is Ken Waters' .375 Express, got up for use in an old Westley Richards Mauser. I suppose the full-length case could be used, setting bullets back to fit the '94, leaving the case body beside the longer bullets empty, if vacant space does help lower pressure.