Well, I had my first KB! yesterday. Fortunately the G20 held strong and just the mag well vented most of the discharge. Also, some came out of the slide/frame gap and made it's mark on my thumb. I THINK pieces of the follower or the top plastic part of the mag that blew off is what hit me in the face...right cheek (I'm a lefty). After I came to my senses and counted to ten on each hand, I started trying to piece together what happened. I was working up a load from the Hornady 7th guide... trying to get 180g MG JHP's to 1200fps with: ~~~ NEW Stock G20/stk bbl with NEW 22# SS RSA NEW Starline brass 180g JHP (montana golds) AA#7 @ 12g w/ CCI#300 LPP seated COAL 1.255" and crimped with Lee FCD Location in FL - ~80-85* and VERY humid; breezy; ~60' ASL (near coast). I have NEVER shot lead rounds in ANY Glock. With 10 rnds in mag, I fired the first rnd @ 1253 fps. Brass case-head was .433" w/ flattened primer BUT didn't hit target (paper plate @ 15y)...I'm not THAT bad. Case had usual Glock bulge for hot rnd out of stk bbl...no smiles or other chamber lines noted. Fired rnd 2. Same results but 1220 fps... no rnd on target, either. The ejected case was in same condition as first. At this point, what was on my mind is why the heck was I not hitting a freakin' 8" target @ 15yds! Fired 3rd rnd which was the KB. It crossed my chrono at 1135 fps. The pistol blew out of my hand fwd about 3-5' and the mag exploded down dumping the remaining 7 rnds around me. The mag is completely 'self disassembled'. After I checked out all the G20 frame/slide/bbl/RSA parts for anomalies, I (maybe foolishly), fired a factory HDY 155g XTP that was in my 'carry mag'. I hit target @ POA at the expected speed of around 1300 fps. I collected everything, packed up and went home to my family, thank God. I think that's all the facts. Any ideas on how i could have gone from a guppied case to a full rupture? Double charges ruled out; no room for powder and/or bullet. No bbl obstruction; previous rnds crossed chrony and cases were recovered and assessed. This IS a max load according to the HDY book I used but it's not the first time I loaded to max...even in .40 in my G23. I'd expect the brass would have shown symptoms of over-spec pressure in previous rnds of that load b4 blowing on me? Any ideas? I attached pics of failed case and factory rnd in chamber. You can see them below on 10mm-firearms.com below if they don't show up here. http://10mm-firearms.com/reloading-10mm-ammo/g20-kb!-ideas-on-what-happened/ - Dave Wanna kill these ads? We can help!