Dumb question as I should know this. Can I put my MK25 (9mm) upper on my factory P226 .40 S&W lower. Locking blocks look the same & the ejectors look darn close. Reason needed is b/c the 1913 rails on the MK25 lower won't work with all of my holster options. Thank you very much!
It's the same Locking insert. The 9mm P226 carries a little longer Ejector.
Some swaps will work and some swaps will not let the slide go on. Give yours a try using the same ejector and if it fits it will probably shoot. If it needs an ejector you can put that on. We can find one of those.