For those accuracy hounds who love to tweak their ammunition to wrangle every possible bit of hair-splitting accuracy, neck sizing the cases is an often employed technique.
This requires a special neck sizing die, which doesn’t resize the fired cases like a conventional sizing die, but only resizes the neck portion of the case. The case body and shoulder are left to the dimensions that the case had after firing, allowing a tighter fit to the chamber, and more consistent placement in the rifle’s chamber.
Please note that this is a technique that only the bolt action can use, as the lever, slide and autoloading rifles don’t possess the camming power to close the breech on anything other than full length resized ammunition.
What advantage does this give the shooter? Well, it makes ammunition that is a near perfect mirror of the rifle chamber.
This means that the ammo will slide back to the same place in the chamber each time, taking as much of the room for play out the equation as possible. The bullet is sent into the rifling from the very same spot each time the rifle is fired, and after all, accuracy comes from repeatable results.
It also saves the life of the brass cases, as only the neck portion is worked and reworked. The shoulder of the case stays firmly in place, and case stretching is even brought to a minimum.
What are the disadvantages? The fired cases can only be used in the rifle from which they were fired. However miniscule, the difference between chambers exists, and if you try to neck size cases fired from one rifle to make ammo for another, you’re asking for trouble.
Another point to remember is that because the bolt action has to cam over the case to get the breech closed, the act of chambering a cartridge will feel more difficult than with standard sized ammunition. This can pose a bit of a problem on a follow up shot, if you use neck sized ammunition for hunting.
For the target crowd, I can say that I feel neck sizing is worthwhile. I’ve seen a significant improvement in group size.
My Ruger Model 77 in .22-250 Remington shot much better groups when I neck sized my ammunition, bringing group size from ¾” to 3/8” at 100 yards.
I also had a customer with a Remington 700 in .300 Remington Ultra Magnum that loved factory ammunition that featured the Nosler Partition 180 grain bullet. He tried to handload that bullet to find the same barrel harmonics and replicate the accuracy (due to the ammo crunch of ’13, he simply couldn’t find his favorite load), but to his chagrin, he couldn’t get it to work.
He called me, and I made him some ammunition with the 180 grain Swift Scirocco II. Close, very close, but he wanted better. I suggested neck sizing the cases, and by George (George who?), we had it! Three shot group size returned to just over ½ MOA, and he was back in business with his long range elk rifle.
If you decide to neck size, make sure you set the die up properly. You want as much of the neck resized as possible to give you proper bullet tension, without moving the shoulder at all.
Use a consistent brand, and preferably lot, of cases and you should see the difference during your next trip to the range.
Enjoy the improved accuracy of hand-tuned ammunition, and gather the necessary information needed to get started with the reloading process. You’ll benefit from this reloading guide if:
- You want to learn how to reload rifle and pistol ammo
- You need to know the necessary tools required for reloading
- You’d like to learn the benefits of reloading ammo