Camel23,
Sounds like your firing pin is pushing the round forward the first time it hits. I'd remove the extractor and see if my round is seating fully in the chamber. Are you firing factory or reloads? You could also be pushing the primer into the brass if it's a reload and the primer wasn't seated properly. The 7-30 case SHOULD be headspacing on the rim, but if the barrel to frame gap is large and the rim is not seated on the barrel, you could be pushing the round forward as it's trying to fire. With the extractor removed, you can make sure the round's rim is fully engaged and then fire it. After firing, measure the case length against an unfired one. How much did it lengthen. If the frame to barrel gap is too large, you will most likely have to send the barrel back to the manufacture. The barrel lug may have been mislocated when they welded it in place, or the frame could be stretched (very rare but possible, is this the only barrel that causes the problem or does any barrel on this frame have a problem).
Bill