Originally Posted by Bill Lumberg
Using factory SAAMI spec rounds, there never was a problem. There has been continual refinement, but not resulting from rampant failure from spec rounds. Older barrels were quite adequate, but not as able to compensate for overcharged rounds or reloaded brass. I've owned and been issued .40 glocks since they came out, and despite heavy agency and personal shooting, never encountered or observed a problem.
The problem was never so much the chamber support as with the ammo. The early Federal cases marked "FC" usually being the culprit. They have long since been withdrawn for the most part, except for a few residuals scattered sporadically in the hands of non LE. There is no such thing as 100% chamber support outside of a revolver as well.
FWIW, I have a new Glock Gen 4 OEM .357 SIG barrel I play with in a Gen 4 G23 and it is superb. To be frank, it shoots just as good as my p229 in .357 SIG.