I have had similar problems with the only set of Hornady Dies I own - also "New Dimension". I bought a set of 6.5 x 55 mm Hornady New Dimension dies years ago and cannot use them due to the fact that they oversize the necks on my cases. After sizing, there is not even enough neck tension to hold the bullet in place! I bought the Lee Pacesetter Dies and never had this problem again! I believe your problem is with the Hornady dies. I reload for .40 S&W also and I use Lee Dies. even after belling the cases there is enough neck tension that I do not have to crimp the bullets in place. You are correct in that a taper crimp is necessary for rimless autoloading ammo because they headspace off the cartridge neck. Revolvers use a roll crimp because they index off the cartridge rim. If you have to rely strictly on a crimp to provide enough neck tension to hold your bullets in the cases, you need to replace those dies because they are oversizing the brass, and a crimp will only provide a small area of contact to grip the bullet. This will affect pressure, accuracy and velocity.
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Last edited by RL357Mag; 08-21-2009 at 03:49 AM.