The failure appears to me to have been in the barrel threads; looks like a standard threaded barrel attachment, rather than the 2-piece design. The fracture surface appears to be brittle, and because the guns were fairly new, fatigue is unlikely. Just a guess on my part, but I'd suspect intergranular stress corrosion cracking. Maybe some bad 400 series stainless, or perhaps some improper thread sealant was applied. Looks like a job for a good metallurgist. Regardless, glad that nobody was hurt and that the failures didn't occur during a more critical event. Very bad PR for our favorite gun company; I hope that you get a satisfactory explanation and that you can share it with us. Thanks for posting. -S2