Thanks Sweetwater. The low velocity bullets had less cartridge neck grip. Fortunately it wasn't enough less to cause a hangfire, like my experiance has given me, and why I've badmouthed the Lee factory crimp for straightwall handgun cartridges. But praise and recommend the rifle dies.
Please let us all know what your results are when not using the factory crimp die.
This crimping thing is really important and many special dies are sold in the attempt to perfect it. In my experience the most damning problem we have with handgun cartridge crimps is varying case length. I refuse to trim them because of the time factor, and have found the best way to get perfect crimps without loosening the cases neck tension from too much crimp on the long cases, is to run the seating die in about one or even two turns beyond what would give a full crimp if the ram is run up to full stroke. I then carefully feel the bullet seat, the crimp contact with the case mouth, and the crimp being formed. When the crimp is complete there is a definite bump as the case mouth hits the bottom of the crimp groove. If just enough pressure is applied to make the case mouth hit the bottom of the crimp groove we have the maximum amount of bullet grip possible, and very consistent. This does leave a variation in overall cartridge length, exactly the difference in case length of the mixed lot of brass, but it has very little effect on velocity uniformity. Far less than variable bullet grip. If I'm unclear in my description of the above and why, write, anyone, and I'll try to fill in the informational cracks a bit better.