Just had a 29/40-120 cato this last launch and blow the forward closure on a G76... Made it up 147 feet according to the altimeter, but here's the funny part. forward closure was gone, never found it, but the threads look fine. Aft closure threads in perfectly, a second forward closure from another case, also fine. I inspected the threads when I got home with an 8X loupe and they look perfectly fine, same as my other case in depth. I'm guess that the sacrificial/weak point in these cases is the forward closure threading. I imagine if I were to uncover that piece I'd see a bunch of stripped threads.