I'll be darn. there are little slivers of aluminum blocking off the vents on opposite sides of the cavity, just like Ian said. One side nice and clean cut, the other side has a tiny burr that I can see under magnification, and it is even more obvious by feel with a dental pick.
So I inspected every cavity of three NOE moulds and deburred them all. Then I took my problematic 5 cavity XCB mould out in the casting shed and went at it. Definite improvement! Many more visually perfect bullets especially as the mould got really hot. I had preheated it on the hot plate and cast fast. After about 100 bullets I added 50 degrees to the melt and soon they were dropping better and better. The last ice cube tray full look to be very high quality. The only disappointing thing is that a vent line exactly intersects the very nose of the bullet. Darn the luck. By the time I give them a tumble the tiny little exaggerated parting line on the nose should be gone.
These good bullets will be processed and carefully loaded along with matching loads utilizing the Lee 312-155-2R. Then I can conduct drop tests and I will report that on the ballistic coefficient thread.
