I work at a range here in the Dallas area. This past Sat (18 Mar), a customer was shooting his W99 in .40S&W. He had fired several rounds and was shooting a few rounds weak (left) handed when it went k-boom. We didn't hear anything out of the ordinary in the shop off the range and only knew it happened when he and several other shooters brought the pistol to the counter, along with two pieces of the upper right grip section, the rear portion of the extractor and the complete rear part of the case. The rest of the case was still lodged in the chamber. This was Winchester factory ammo which he brought (not ours) and not reloads. The shooter was uninjured, but had he been shooting it with his right hand, he probably would have had some serious hand injuries.
Most of us that work here have many, many years experience (I have well over 50 years) and had not seen a k-boom involving a polymer frame. We average about 2500 NEW shooters a year that use our range and have many members and returning customers, so we do see a lot of shooters and guns.
We advised the customer to 1) not do anything to the pistol (work the slide, take that case out of the chamber, etc.) just leave it as it was, 2) take lots of pictures, including close ups, from every angle of the pistol and ammunition with a digital camera 3) inlcude a card in every photo (as best could be done) which displayed the date, time, Model number, serial number and ammo lot number, 4) to call Winchester (Olin) 5) to call S&W (the US importer/support center for Walther products) and 5) to follow up the calls with e-mail and/or snail mail with a CD containing the photos.
This was NOT a matter of an unsupported section of the case blowing out. The entire rim section of the case came off cleanly.
Anyone else have a problem with their W99 or is this another event that adds to the issue of k-booms involving the .40S&W?