A voluntary recall on the recoil spring assembly of Gen 4 Glock pistols started on September 6 and affects all Gen 4 pistols except the G26 and G27.
Several department armorers forwarded me a copy of the notice sent out by Glock. The announcement states Glock has initiated a voluntary exchange program for the recoil spring assemblies of every Gen 4 Glock sold before July 22, 2011. While Glock does not cite any specific problems with the original recoil springs, the memo does indicate that the assemblies have been modified to “…ensure each pistol’s performance meets the company’s demanding standards.”
I’ve heard of various people having problems with the 9mm versions of the Gen 4 guns, and it was speculated that the new, stronger recoil spring assembly may not be reliable with standard pressure 9mm ammo. However, the problems did not seem to be universal.
Regardless of the reasons, you should contact your department armorer or contact Glock for all of the details on the exchange. The exchange is free and you do not need to ship anything back to Glock.