May 19, 2022 by Sierra Bullets Ballistic Technician Paul Box
Neck tension is a key factor in building accuracy loads. It controls the bullet’s grip. I think most reloaders take this for granted and don’t give it enough thought. I have had the best accuracy overall with.002? The neck tension. You will occasionally run into a rifle that prefers something other than.001? Or even.003?. But.002??. It worked well for me. How can we control neck tension? Let’s look at how to control neck tension. For starters, I prefer an expander ball with a diameter of.003. The bullet diameter is smaller than the expander ball. For example, in a.224 caliber, you could run an expander ball of 0.221?. To reduce the diameter of the expander ball, simply chuck your decapping rod assembly into a drill and turn it with an emery cloth. Once you have the desired diameter, polish it with three or four ought steel wool. Tips for Dies with Interchangeable Neck Bushings
If you are using a bushing tool, I measure across the necks of eight to ten loaded rounds. Then, I average these and calculate.003. Below that measurement. You can find other methods to determine the bushing size, but this method has worked well for me. Proper Annealing Can Deliver More Uniform Neck Tension
Annealing is another thing I want you to know. Brass that is at the right softness will take a “set”, which is better than brass that has become too hard. Brass that has been worked to a point will be more springy when it comes from a sizing machine. Neck tension will vary. Did you ever notice that some bullets are more difficult to seat than others? This is why you need to pay more attention to neck tension. It will help you get better accuracy and more consistent groups.
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