I thought I should take some time to explain my disdain for Glock... and to provide some contrast... I'll also explain why the Steyrs I own are demonstratably superior in every way.
First.. you need to understand that the Glock was designed as a 9mm. When they decided to offer it in .40... they had a choice... redesign the whole weapon... or find some way to rig it.
Guess what they chose?
That's right. They simply rebarrelled, modified the breech face, and dropped in a stiffer spring... and called it a Glock 22... or 23... depending. In fact... many manufacturers have done this... including S&W... with the S&W 99.
We call this bastardization an Unsupported Chamber. If that sounds bad... its because it is. In unsupported chambers brass expands far to much... and is even mishapen... most commonly expanded oval.. pushed down in the 6 o'clock position. Brass fired from an M40 measures between .428 and .430. Brass fired from a Glock 22 measures .431 to .433. That's a huge difference... as anyone who reloads can tell you.
Look inside a M40 sometime. Side by side with a Glock 22 you'll notice right away how much beefier the Steyr is. Because again... the Steyr was designed to be a .40. Not a 9mm.
The simple truth is... you don't want to reload brass that was fired from an unsupported chamber... and you want to be very careful about what loads you put in that chamber... lest you learn first hand why we use the term KaBoom.
I'm not trying to panic you here. If you're shooting factory tested ammo... you're obviously fine. But you should think long and hard before you start rollin' your own for your Glock. Glock isn't interested in making sure your brass lasts. They apparently only give a damn about rigging up half-assed designs that function... sort of.
The only good thing about glocks is the fact that you can't swing a dead cat without hitting one. Consequently ammo manufacturers have beefed up their cases to attempt to deal with the flaws in the 22 and 23.
How pathetic is that?
And now for a little background. The Steyr M4o was designed by a former employ of Glock... Wilhelm Bubits. He was around at the begining... and was extremely critical of the 22 and 23 designs for the reasons listed above. He was so frustrated with Glock's designs he actually became a designer himself and presented his copyrights to Glock. Glock didn't like the M40... so he took it across the street to Steyr.
They loved the design... and after some tweaking put it into production. The result was the most impressive modern pistol that no one gave a chance.