I have a gen 2 G23 that I bought 12 years ago. After about a year of shooting it, I noticed something I was not comfortable with so I bought a Wilson guide rod and spring. It was a non-captive spring, and quite a pain in the ass, so a couple years ago I switched to a captive Lone Wolf SS guide rod and an 18lb flat spring from springco.
Now, the "something" I was uncomfortable with was that I could put my thumb on the barrel where the ejection port is, and unlock the gun just by pushing down on it. I have tried this with every other handgun I have handled, and it has never happened except with some Glocks. Usually they are the 9mm and .40 cal Glocks. Not every Glock, but a few of them.
ETA: When I noticed this problem, I had only put about 1500 rds through the gun. I mostly shot the 9mms I owned at the time. There was also a significant amount of case-bulge on the brass from firing my g23 with the factory guide rod and spring
I still have my original factory captive unit. Here it is compared to the captive LW rod with the 18lb spring, the LW is the bottom one:
Now, I have unloaded the gun, and installed the factory unit. I hold it with my thumb on the locking part of the barrel like so:
I push down with my thumb, and now the action is unlocked:
The Wilson rod I initially installed to correct this problem was excellent. It was impossible to do the same thing with it in. My G23 ran flawlessly for the next decade with it in, and when I decided to get a captive unit I found out the Wilson rod used an 18 lb spring. This is the reason I went with the 18lb spring for the LW rod. No case-bulge for the most part.
I haven't had any problems with my G23 with the LW unit either.
I am posting this because someone mentioned that there is no need to replace the factory recoil rod, and I guess thats true most of the time.
I still recommend that people purchasing a Glock perform this simple "thumb test" when they purchase one.