Sorry for the delay, I've been quite busy lately. Seems the problem was appearently as suggested - the empty cases hanging up on the case mouth. After re-shaping the hammer face it fired every round! The rifle is still unfinished however as proofing resulted in slight movement of the right barrel due to too shallow threads (or would that be too deep?). A dumb mistake I should have caught!!!

The barrels are attached by way of a bushing or sleeve, threaded OD to match those cut on the ID of the monoblock and ID to match those cut on the OD of the new barrels... confusing? Has to do with utilizing barrels laying around the shop that weren't quite large enough to thread into the mono block directly. Except for my unforgivable sloppy threading the method should be quite safe.
I removed the barrels and set them back a bit with new threads per barrel then "HighForce 44" soldered them just to be sure. Need to re-cut the extractor notch and chambers before any more testing but wont have time for that till at least next week sometime.

The above makes me sound just able enough to create trouble doesn't it?

I swear I'm not normally so sloppy. Guess anyone can make a mistake although such "mistakes" in gun work can have dangerous and unforgivable consequences!!!