So, I'd made up a 100 or more 11.2 BD under 180 XTP rounds for my Glock 6" factory barrel. Testing in the past said this was safe in this barrel. I'd checked to see that my 550 wouldn't throw any exceptionally high loads that I'd have to worry about op. Well... trip to the range. Fired some rounds over the chrony and was seeing inconsistent speeds... lowest I think was 1290. What made me take notice, though, was when i saw 1600 in the bunch. i stopped firing and started looking for brass (range hasn't enforced pickup for a while... so scrubbing through 40 and 45 cases in the natty undergrowth and grass was a pain. Found some of my cases... including 1 with a blown smiley, and 2 more with obvious smileys. Something in all my hot load development I'd never seen before with this barrel. This is all multi-reload brass, so I'm sure I just asked too much of it. Gonna pull them all, and reload with around 10.5 grain BD. Fun stuff. Oh... also learned I was getting damn near the same fps from my 4" with this stuff as the 6"...and it has a looser chamber than the 6"