Ok, thanks for the great info. I have a P229-1 barrel sitting around since I replaced it with a threaded barrel and was just wondering. I don't want to purchase a conversion barrel so I'll just keep looking for a new/like new P229 ASE 9mm. I have one already but thought a second one would be nice to have. But I'm actually looking for a LNIB/NOS P226 Platinum Elite 9mm so I'll concentrate on trying to find that gun.You need a "conversion" barrel or a complete 9mm slide.
A P229-1 barrel will not work in a .40/.357 slide.
I also have a Bar Sto 9MM conversion barrel for a P229. I just use the 40 cal recoil spring and it's been perfect, I didn't have to change it.Personally I would get Bar-sto .40S&W to 9mm conversion barrel and some 9mm mags with a 9mm spring and 2nd recoil rod
Did that with .40 legion 229