I have a Sig320 FS 45acp. I bought mine before Sig came out with the MOS version of the same ... somebody told me that I could just get a slide from Sig that is cut for an RMR. Does anyone know if that's true and if so is it only compatible wit the Romeo RMR.
Okay, I see what's going on. That's a lot of confusion to unravel.
MOS is mounting standard and a set of adapters for Glock, which allows to mount various sights, such as RMR, SRO, DPP, and so on.
RMR is a red dot sight made by Trijicon.
Romeo is a brand of red dot sights by SIG.
So, there is no such thing as "SIG with MOS version" of whatever, because MOS is only for Glocks. Equally, there's no such thing as "Romeo RMR", just as there's no such thing as "Silverado F-150".
What you
appear to want is a slide for a SIG in .45, which is cut for an optical sight. Unfortunately, I know of no such. SIG's factory slides with optics cuts are only compatible with 9mm. I think your best bet is to send the slide away to Suarez to be milled.