Does anyone know if a P-09 barrel will fit in a 2014 P-07 slide?
Yes. I briefly owned a 2014 P-07, and did some parts interchanging with my P-09 on the table for fun. I never shot it in this configuration, mind you, but it does physically fit and appear to function correctly.
The recoil springs are exactly the same between the two. I have replaced my P-09's spring with an ISMI 13# spring for a Glock 17. Works beautifully. I tried this same spring in my P-07, but it was still ever so tight (the slide). My wife couldn't rack it. She can barely rack the P-09, but she didn't like the P-07. So it got sold.

