Sig P239 .40 S&W to 9MM Conversion

[LubeckTech]

I work with someone who is interested in converting a .40 Sig P239 to 9mm by installing a 9mm barrel.
I am thinking the magazines would have to be replaced along with at least the extractor or possibly the entire slide. Anyone ever done this conversion?

 

[Sir Aardvark]

I have a Bar Sto conversion barrel for my .40S&W SIG229 which enables it to shoot 9mm.

Everything works the same - I didn't have to change anything other than the barrel - same magazine, same extractor, same spring - it all works good. I'm sure it would be the same for the 239