[b said:
Quote[/b] (andrespeng @ June 06 2005,6:59)]What is FULLY supported chambers?
My understanding of it is how much of the case has nothing around it. On some guns, if you take the barrel out and stick a round in, you can see part of the side of the casing right above the feeding ramp. Glock probably does this so they do not have to use as sharp an angled feeding ramp in a confined space; thus in theory more reliable feeding with most ammo types. What can happen is that the round will not be in perfectly and when it goes off, the pressure is so great that it comes out the bottom where the small exposed casing is. There will always be some exposed area for the extractor to grab on, but on fully supported chambers this is just for the rim and is uniformly the same all the way around. In guns like this, even if something goes bad, the path of least resistance is going to be the bullet and not the casing. Broken case extractor tools for the AR15/AK/SKS lend one to think that a case blowing its back off is not a big event like it is on unsupported chambers.
EDIT: Going KB without overloaded ammo is usually only an issue with guns that have the feeding ramp integrated with the barrel (as with most/many autoloading centerfire handguns). The unsupported chamber in guns like Glocks can actually contribute to out of battery discharges especially since handgun rounds are really not that long and tend to not guide themselves as well as rifle rounds. IIRC the P99 has an out of battery safety built in. Glocks have several points of failure in that an overloaded round (dangerous in any gun) is more likely to blow off the exposed side of the case, a case that just has some metal flaw in the back (shit happens when factories roll off a million a day), and a round is more likely to blow off out of battery when the feeding ramp shortens the distance where a round can guide itself in.
I really wish I could inspect a P99 now and take some pics, but unfortunately mine had a screwy slide and had to be sent back as defective. SW/Walther America is being very cool about it and sending me a new one (whole package, so 2 free mags!!).