I was at the range with a buddy last week and one of the pistols I brought along was my Witness in 9 x 25 Dillon. We both enjoyed shooting it and he ask me if his large frame Witness which has a 357 Sig barrel fitted could be reamed to 9 x 25 Dillon with a 357 Sig reamer (another buddy has one). I told him I don't know so I thought I would ask here. Measurements on most dimensions look to be just .001 off except for about .125 in length I believe. Again I have no idea.

Steve.........

No. The neck and all that shit will be off.
Rent a 9x25 dillon reamer and do it that way.

I found an outfit that sells 9mm barrels for the witness and reamed a 9mm barrel to fit after fitting it to the pistol.
So I have a witness in 10mm with a 9x25 barrel to boot.

4Dreamer rentals.

I was kind of thinking that but wasn't sure and I didn't want to offer him any advice until checking around. About 5 years ago I did rent a 9 x 25 reamer and did my Witness barrel and also a 9mm Blackhawk cylinder I had at the time. It seems really loud in the Blackhawk. I wouldn't mind having a 1911 barrel in 9 x 25 to go in my Delta Elite or Ruger 10 mm.

Steve........

Well there might be guys that have done a wildcat but then where would you get the dies?
I also read about guys throating the 357sig and loading long.
Then handloading hot.

Buddy barely knows how to handload much less do any wildcatting. After the Holidays I will look for a 9mm barrel for my 1911 with the right size hood and rent a reamer and do his barrel at the same time.

Steve.......