I am trying to upgrade my sights on the P320 M18 and I bought some VTac sights, it said they were 320 compatible but now that I have them it doesn't seem they will fit. Has anyone mounted new sights on the M18?

Welcome to SIGForum.

I believe the P320 <> M18 for rear sights.

Did you get the variant with the rear sight integral to the optics plate? If so, pretty much no standard (SIG design) rear sight will work with that model, fronts will though. Looks like Bobro and maybe a couple other companies make optics adapter plates with rear sights. I'm sure that's probably not what you're wanting to hear...

https://www.bobroengineering.c...REAR-SIGHT_p_51.html

Edit:
Looks like Dawson and perhaps Apex has some options as well:
https://dawsonprecision.com/sights/sig-sauer-sights/

That is what I was afraid of, there was nothing on VTac or GGIs website and no videos of it being done that I could find Thank you!