A Cowboy quick draw friend of mine explained this is most likely caused by the cylinder being out of time with the barrel when it goes off. He has witnessed this several times when quick draw shooters try to get a quicker shot off by changes in springs and other adjustments. It is also a possibility the new gun was not set up properly from the factory, 1st shot was lined up then cylinder rotated to wrong place and fired 2nd one which went POW. Just like the old story of mud in the barrel of a shotgun which blows up in your face. If you notice the picture from the top, the cylinder is not in line with the barrel and the stopped bullet pressure has no where to go but up.