Q: I want to put a cannelure on large calibre rifle bullets which will enable me to crimp the case mouth into it so that they'll not be pushed back into the case during feeding and by recoil. I've also heard that a cannelure helps lock the jacket and core together and prevent core and jacket separation. Some of the bullets I use don't have cannelures, and others have them in the wrong place for seating the bullet close to the rifling lands. I thought I would buy a cannelure tool which would allow me to put a cannelure wherever it is wanted, but a mate says it is not a good idea to put cannelures on bullets as it can ruin accuracy and affect expansion. If this is true why do factories put cannelures on some bullets?
A: Bullet manufacturers are able to produce a controlled cannelure that is rolled to precise depth with very uniform pressure, and they can design the cannelure tool to be compatible with the jacket design. They can also design the jacket for a specific type of cannelure at a specific location. Some cannelure tools available to the reloader roll a very sharp-edged groove into the jacket and if it is too deep it can weaken the jacket and cause it to fracture during expansion. Rolling a cannelure into the bullet jacket causes metal to be displaced distorting the bullet. While I have some doubts that a home-applied cannelure would ruin accuracy, the secret is not to overdo it. Don't apply the cannelure with too much force or too deeply. Try to develop a technique for applying the cannelures uniformly to each bullet. Don't depend on the cannelure to lock the core and jacket together as in my experience this effect is minimal. If you are using a rifle with heavy recoil, you'll need a cannelure, but bullets for these cartridges have very thick jackets and rolling a cannelure on takes a lot of force, more than can be applied with the inexpensive cannelure tools available to the handloader. My advice is to buy a factory bullet which has a cannelure in the right place.