The gun is 5 yrs old. I noticed the newer ones have a longer flange where it attaches to the barrel at the weld point. This must have been a problem they were aware of although it probably rarely occurs. The steel duck loads have very high pressure which is probably the cause but it still shouldn't happen.
I thinks I can fix this by applying flux and solder ahead of time then clamping in position , then heat the flange..
Thanks for your input
Jim