Just to expand a little, here is text I saved from a forum message. Unfortunately I didn't log the forum or the poster
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a good friend of mine who now lives in Switzerland who was over for the Holidays. Says that he is hearing that there has been a large refit of various Austrian Police and Military units as a result of the Glock frames going brittle from prolonged exposure to the elements and as well as age. Now he is not a handgunner, and is a member of the civil defence force (or whatever the guys who hand out gas masks and say, "Go this way to the shelter!"). Anyhow he does work for a rather huge company, and said he heard this from some of the security personal who also carry Glocks. They too had been instructed to change out guns. I have asked him to see if he can get any photos or written documentation on this and send it to me. As yet I have not, but he only went home a week and a half ago.
To further discuss this (yes I know it is OT somewhat, and I actually like Glocks alot so I am not a Glock hater, but I do have a lot of experience with plastics and polymers. In the industry I work in we utilize a lot of both plastics and polymer based products, all of which must be able to stand up to sustained exposure to sunlight, cold, heat,rain, and stressing. The longest lasting of either of these materials is about 6 years. Now the exposure is constant, Everyday, all year. As season change etc somethings do increase or decrease, more rain less rain etc. Millions of dollars and 40 years of research has yet to yield us a single AFFORDABLE product that can stand up reliably to these conditions for more than 5 or 6 years. These conditions are similar to those that a carry or duty gun would be exposed to, and so it is only natural, for me at least, to believe that this could happen to a Glock as well. I have also seen some of the products we use sit in a room never used, never really exposed to the sun, nor rain, nor stress, nor any real hot or cold conditions, but still be just as brittle after a few years, just from sitting in a dark closet.