I also have a Lone Wolf Dist. 40-9 conversion barrel... has been pretty much awesome for me.  It's always great for cheap (and easier) shooting at the range, as generally 9mm is always cheaper on the shelf than .40 S&W and produces less felt recoil to let  you plink away easier.

 

The reason it's not the universal panacea is because it does affect your shooting results.  The lower bullet weights of the 9mm usually will result in you shooting high when using a 40-9 conversion barrel in your Glock.  The gun is sighted at the factory and is built to be shooting .40 S&W, generally the 180gr load , but then you put in a different barrel with completely different ballistics, and you'll see a lot of high hits on your target.

 

That DOES NOT Mean you shouldn't do it, it's easy to compensate and some people will not experience this apparently.  But it is an issue and of course it will never be 1001% perfectly reliable as the standard setup.

I have a KKM conversion barrel for my G22 and it works great.  Well it does now, at first I had lots of issues.  Evidently it is all you need in a Gen3 Glock, but in a Gen4 you need to switch the recoil spring when you use it to a G17 spring.  Once I did that I never had an issue.  Some have even fed the gun 9mm rounds with a .40 cal magazine, but that is not going to be as reliable as using a G17 magazine as well.

 

Again, much depends on what the purpose of the gun is going to be?  You have not told us that.

Have you considered a Glock 24? 8.07 inches of sight radius.

Correct me if I'm wrong but the G24 (and I believe the 17L) have been discontinued awhile back.

Correct me if I'm wrong but the G24 (and I believe the 17L) have been discontinued awhile back.

Don't know about the G24, but the 17L is still in production but on a limited basis.  This past fall there were lots of ads from the big dealers for them as Glock must have done a big production run of them.  The 17L is a great gun, but not legal for many competitive shooting competitions.  It certainly does not fit into and IDPA sizing box