Paul Box, Ballistic Technician at Sierra Bullets, October 8, 2023Neck tension is a key factor in building an accurate load. It’s one of the factors that determines the “grip” of a bullet. I think that a lot reloaders take this for granted, and don’t really give it much thought. So, how much neck pressure is enough?I’ve found that over the years, and with a variety of calibers, and burn rates, I have had the best overall accuracy with.002? Neck tension. You will come across a gun that is best with.001? You will run into rifles that are best with.001? It has worked well for me. How do we control neck tension? Let’s look at it.First, if you are using a standard sizing tool with an expander, simply remove your decapping assembly from your die and measure the ball. What I prefer to start with is an expander ball that’s.003? The expander ball should be.003? smaller than the bullet diameter. For example, in a caliber of.224, you would run an expanderball of.221?. If you need to reduce the diameter of the expander ball, simply put your decapping rod in a drill. Then use some emery fabric to turn it down. Once you have the desired diameter, polish it with 3 or 4 ounces of steel wool. This will give your case a mirror finish, and reduce the drag that comes through after sizing.
If you are using a bushing tool, I would measure the neck of 8 or 10 loaded rounds. Then, take an average and subtract.003? There are other methods to determine bushing size, but this system has worked well for me. This system has worked for me. There are other ways to determine bushing sizes, but I have found this one to be the most accurate.
Annealing is another thing I would like to mention. Brass that is soft enough will “set” better when it comes out of the sizing tool than brass that is too hard. When brass is work hardened, it will be springier when it comes out of the sizing die. The neck tension will also vary. Have you ever noticed that some bullets seat harder than others? This is why.Paying more attention to neck tension can give you better accuracy and more consistent groupings.
Tags: Bullet Release Force, Sierra Bullets, Neck Bushings, Reloading
