The ticking time bomb that is the recoil spring
It is hard to beat a Glock of any generation when it comes to reliability, but it comes as a shock to many that inside their slide hides a pitfall to the whole program that the savvy polymer pistol user can easily overcome.
Like a 5,000 round failure point…

One of these things are not like the other– but both need to be evaluated at/near the 5K mark! Here we see a Gen 3 Glock 19 factory recoil spring assembly compared to one for a gen 4 Glock 22
The standard Glock factory guide rods are (this should come as no surprise to you) made from polymer. While low-cost and easy to produce, these plastic guide rods can chip, crack or break resulting in feeding or ejection failures. Further, these guide rods flex to a degree when in operation, which many argue will contribute to accuracy problems due to poor consistency. Finally, they have been known to snap, leaving the pistol inoperable. This weak link can be alleviated by putting some heavy metal into the mix.
More in my column at Tac.44.com