Originally Posted by JonM
crimping bottlenecks can easily cause the case mouth to lose tension on the bullet resulting in longer bullet runout or setback due to lack of friction.
needing a heavy crimp on heavy recoil rounds or tube feeds is a myth. if you do crimp be sure your using the correct crimp for the bullet. cannelures are for roll crimping bullets without roll crimps should be taper crimped only.
crimping is the biggest misunderstood myth riddled part of ammunition loading i can think of.
You forgot it include the third and most effective crimp for Bottle necked rifle rounds, The Lee Factory Crimp die. It is not a taper crimp or a roll crimp but a collet type crimp.
The LFCD not only helps secure the bullets (Cannelure or no-cannelure) it improves accuracy in my semi-auto loads.
Here is a little test. Three rifles, three different cartridges, 50 rounds each. All three showed improved accuracy with the use of the LFCD.