It seems to get asked every other week on every gun forum so here is a short explanation of 40 S&W Glocks:
I've been a Glock armorer at a medium sized police department for 12 years and carried a G22 for a chunk of that time. I've run the gambit with Gen2 and Gen3 G22's. There are two main issues.
With the Gen2 G22's Glock essentially took a 9mm G17 frame and slide and bored it out to 40 S&W. They didn't account for higher pressure and didn't put enough case support in the chamber of the barrel and if you ran extra hot ammo OR you had ignition without the gun being completely in battery (which was extra likely with a G22 because the recoil spring would wear out faster due to the higher pressure ammo) you would blow up the case and possibly the gun in the process.
Glock began to correct these issues in the late Gen2 guns and early Gen3 guns. They changed the chamber specs and added an extra pin in the locking block of the frame. Some people will tell you the extra pin was superfluous. On 40 S&W Glocks I see that metal pin break fairly often. So, I can tell you that there is extra stress going on in that area of the gun and here is why…
In Gen2 and Gen3 guns the 9mm and 40 S&W use the same recoil spring assembly (RSA). Weird huh? Sig and most other brands have a different spring between those two calibers. Not Glock. The 40 S&W guns wear out RSA’s faster pure and simple. As the RSA wears out the plastic frame of the 40 S&W guns really begin to absorb a fair amount of recoil. That flexing ends up placing stress on the locking block and breaks the pin. But wait, there’s more…
When WML’s came out most were plastic. I remember around 2000/2001 when the Gen3 guns were arriving and every cop went out and bought a M3 light and a pouch for it on their belt and would draw their gun and stick it on and think they were cool (some things only look truly stupid in retrospect). Those plastic lights like the M3 and the Glock light didn’t fit super tight and their plastic bodies allowed some flex during recoil. Enter the X200 and TLR 2005ish.
Some guys started seeing feeding issues with the M3 light. When the X200 and TLR came out some really big feeding issues started to show up. What was happening is the metal light was rigid on the dustcover of the frame and wouldn’t allow it to flex. On a TLR where the light mount tightens, the issue was even more pronounced. So if a guy ran a metal light on a brand new G22 he was cool for about the first 1200 rounds or so. Then the issue started to pop up.
Few things going on:
1) No flex in the frame meant the RSA took all the recoil wearing it out faster.
2) Worn out RSA meant most hot duty ammo (like Federal HST) would cycle the gun, but practice ammo would not. Why? The higher velocity ammo would cycle the slide fast enough to function, but would beat the gun to death evidenced by peeing and a broken locking block pin.
3) The Gen3 magazines would also flex around more during recoil and the rounds would tip up in the magazine. So the slide isn’t going at the right speed and the rounds are being presented almost vertical. You end up with a classic failure to feed.
There was a lot of back and forth and denial between Glock and the LE community a lot more shenanigans and then some of us on both sides figured it out. I loved the guys that would run the light until the gun started to FTF and then take the light off and declare everything fine. Little did they know the RSA was now toast and the gun would run because the frame was taking the impact and the gun was beating itself to death. All those guys ended up with broken locking block pins and other issues. Same with the guys that said, “I’ll just shoot duty ammo because that seems to work.” Same deal.
Glock went through several new magazine followers and springs before they finally introduced the Gen4 guns with a new magazine design. They look very similar, but even the first Gen4 G22 mags that came out got it right. But magazines alone don’t solve the problem. So here is what you have to do…
If you want to carry a Gen3 G22 with a light here is the solution:
-Change your RSA every 2500 rounds or so
-Use the latest Gen4 Glock magazines. When mags start to go south dump them for new ones.
-Check the locking block pin once a year to make sure it’s still intact
It is really that simple. I have well over 30 guns in service that couldn’t get through one mag without at least three FTF’s that run flawlessly with that prescription.
Glocks in 9mm and 45 ACP don’t suffer the same issues because the pressure of the rounds is so much less (and different) than the 40 S&W. My department only issues the 9mm round in +P (duty and practice) and I can tell you it won’t wear out the gun anywhere near the way 40 S&W does. I still change the RSA’s on my own 9mm and 45 ACP guns fairly often though. They’re dirt cheap and extra insurance that everything will keep rolling.
I’ve seen a few G21’s that started to develop FTF issues. Simply changing out springs, both RSA and mags, has always solved the issue. Remember, gun springs are like the oil filter on your car. They aren’t meant to last the life of the car or gun and need to get swapped fairly frequently.