Hi, I ran across a 9mm P320 minus the FCU at a good price locally. Before I buy it, I just want to confirm my P320 45acp FCU will work with it. I have read that dimensionally 9mm and 45 FCU's are the same but internally the 45 FCU is slightly different. Do I need to modify or buy anything to get them to work?

I don't know whether they can be modified to work or not, but I was talking over .45 FCUs with SIG CS a couple of days ago and the CS guy's comment was that .45 FCUs (at least as-is) will not work with 9mm/357SIG/.40S&W.

Per this 4/12/2019 post, yes it should work. I personally have not done it, just providing the info.

"Yes, a P320 45 ACP FCU can drop in a 9mm/40Cal grip module and function with slide and magazines. It does not work in the opposite direction, in other words, a 9mm FCU won’t function in a 45 ACP. I’ve run my 45 ACP FCU in my 9mm exchange kit with zero issues and hundreds of rounds."

Full Link:
https://sigforum.com/eve/forums...0601935/m/2970053354

I presume they are of the same Gen re the slide lock lever. See this link if necessary:
https://sigforum.com/eve/forums...0601935&m=1370004124

Thanks for the replies. I think I will have to upgrade to the new style slide lock.

My understanding is they don’t Market it as acceptable because doing this disables the “takedown” safety. Functionally it will work fine. If I had known this years ago all my fcu’s would have been 45.