You need to buy a .40 or .357 then convert to 9mm. I have a Gen 3 Glock 35 and a Gen 4 Glock 22 and have Lone Wolf barrels in 9mm and 357. I've actually used the 40 mags to fire 9mm and it works fine, but have aquired some 9mm mags as well. The nice thing too about the 9 barrel in the 40 is that it has a larger bearing surface and locks up and shoots better. I let a young man who was thinking about a Glock to compete with, shoot my 35 with the 9mm barrel in it last night and his shots touched each other at 25 yards when he tried it to see where it shot for his sight picture. You can use the standard recoil spring also and it will work well as long as you use full power loads. My Gen 3 I had to go 2 pounds lighter with my 9mm handloads but the Gen 4 works fine with the standard spring so far.
Glock Lone Wolf 9mm conversion with 40 cal mags - YouTube

Thank you so much, very informative. I guess I'll be going for the G23 then.

Just picked up a Gen4 G23 myself. Haven't shot it yet but already thinking about the LW 9mm conversion barrel. I know the new 40's have had fewer growing pains than the Gen4 G17/19 have had. My one pause on picking up the conversion barrel was the stock Gen4 G23 spring assembly successfully pulling double duty for both chamberings. Encouraging to hear some positive first hand experience that it can. Looks like I need to order a barrel and hit the range.

One thing I found with the Lone Wolf barrels is that they sometimes need a few hundred rounds to seat in properly and give best accuracy so be patient. All of mine shoot very well.

Originally Posted by rgrundy

One thing I found with the Lone Wolf barrels is that they sometimes need a few hundred rounds to seat in properly and give best accuracy so be patient. All of mine shoot very well.

Agreed, my friends G23 w/ LWB seemed to not work the best at first

This was the reason my brother just got a G19

G23= accurate as hell
G19= SUPREME GOD ACCURACY

The 40-9 barrel in my Glock 35 took several hundred rounds to seat in and now it cuts bullet holes. The 40-9 in the G22 shot 1.5 inch groups at 25 yards after 20 or 30 rounds and continues to do so. The 357 barrel shot 3/4 inch groups right out of the box and contiues to do so. The G35 original 40 barrel will do an inch and the original G22 barrel will do 2 inches on a good day. For $100.00 apiece (from Dillon) they are well worth the price. You can use lead bullets with them, which you can't do with the Glock barrel and they support the cartridge better so you can reload the brass and get good results which you can't do with the 40 Glock barrel especially. The cases are usually bulged and won't resize properly.