Porkfrog, I came across that assertion many times while researching various gun items. Google for .40 cal Glock chambering or something like that and you'll find many references.
Here's one, not the best, but typical:
(quote) In the end, I was leaning towards the Glock. My only issue is that in the .40, the Glock chamber is not fully supported. And while Glock owners will tell you that (It's not an issue) it is if it's my hand that might get a case failure on upwards of a kb!. This is especially true in the .40, the 9mm and .357Sigs all have supported chambers, but not the .40. So I would buy a Glock but for the fully supported chamber and spongy trigger. They say that I can get a new barrel from BarSto that is fully supported, but then that would put me in the price range of a Sig, and then why wouldn't I do that? They also say that I can shine down the internal trigger parts and make it a lot smoother. (unquote)