Reloading 30-40 Krag question.

[Patrick Chadwick]

Yoopercollector, however you spell cannelure, don't crimp. Parashooter put it quite succinctly.

Let's think this through:
Crimping bends in the mouth of the case. Sharply, with a roll crimp, or more gently, with a taper crimp.
In BOTH styles, the amount of metal forced into the bullet will be more - if the case is longer - or less - if the case is shorter.
In other words: the extraction force when the bullet is fired will vary with the case length!

As far as I can see, if you crimp, then you must have a very closely controlled case length to maintain any kind of consistency of the extraction force.

In other words, crimping produces yet another variable to affect your groups!

As Parashooter wrote - you don't need it, so don't do it.