GLOCK, INC. Technical Bulletin #920403
April 1, 1992
Glock, Inc. announces a production change of the firing pin safety system. This new firing pin safety system has been installed in all production Glock pistols since November, 1991. A voluntary upgrade is being offered to maintain the Glock tradition of ensuring that all of our pistols are up to the latest standards in 21st century Glock technology.
Most importantly, the components of the new firing pin safety system are not interchangable with the components of the old system and Glock will always strive towards maintaining this feature of interchangability while working to ensure future interchangability.
The upgraded firing pin safety system consists of: the firing pin, firing pin safety, the extractor, the spring loaded bearing and the trigger bar. The upgraded system is applicable only to Glock pistols with the following serial number ranges :
Glock 17 - alpha prefix AA - WF