January 20th, 2019

Reloading Bench — How to Optimize Case Neck Tension

Case Loading Neck Tension Sierra Bullets Paul Box

by Sierra Bullets Ballistic Technician Paul Box
One thing that plays a major role in building an accuracy load is neck tension [one of the factors that controls the “grip” on a bullet]. I think a lot of reloaders pretty much take this for granted and don’t give that enough thought.

So, how much neck tension is enough?

Thru the years and shooting both a wide variety of calibers and burn rates of powder, I’ve had the best accuracy overall with .002″ of neck tension. Naturally you will run into a rifle now and then that will do its best with something different like .001″ or even .003″, but .002″ has worked very well for me. So how do we control the neck tension? Let’s take a look at that.

First of all, if you’re running a standard sizing die with an expander ball, just pull your decapping rod assembly out of your die and measure the expander ball. What I prefer is to have an expander ball that is .003″ smaller than bullet diameter. So for example in a .224 caliber, run an expander ball of .221″. This allows for .001″ spring back in in your brass after sizing, and still gives you .002″ in neck tension. If you want to take the expander ball down in diameter, just chuck up your decapping rod assembly in a drill and turn it down with some emery cloth. When you have the diameter you need, polish it with three ought or four ought steel wool. This will give it a mirror finish and less drag coming through your case neck after sizing.

Tips for Dies With Interchangeable Neck Bushings
If you’re using a bushing die, I measure across the neck of eight or ten loaded rounds, then take an average on these and go .003″ under that measurement. There are other methods to determine bushing size, but this system has worked well for me.

Case Loading Neck Tension Sierra Bullets Paul Box

Proper Annealing Can Deliver More Uniform Neck Tension
Another thing I want to mention is annealing. When brass is the correct softness, it will take a “set” coming out of the sizing die far better than brass that has become to hard. When brass has been work hardened to a point, it will be more springy when it comes out of a sizing die and neck tension will vary. Have you ever noticed how some bullets seated harder than others? That is why.

Case Loading Neck Tension Sierra Bullets Paul Box

Paying closer attention to neck tension will give you both better accuracy and more consistent groups.

Permalink Bullets, Brass, Ammo, Reloading, Tech Tip 1 Comment »
January 20th, 2019

The .20 Practical AR — Wicked Accuracy, Low Recoil

20 Practical AR uppers

The new .224 Valkyrie for AR15-platform rifles has garnered lots of attention lately. That new cartridge has gotten people thinking about the options for an AR shooter beyond the venerable .223 Remington (and 5.56x39mm NATO). While the .224 Valkyrie is good for shooting long heavy bullets (such as Sierra’s new 95gr SMK), there is a simpler, cheaper option for folks who favor “fast and light” — smaller, lower-mass bullets traveling at very high velocities. That option is the 20 Practical, which is simply a .223 Remington necked down to 20 caliber. This little cartridge can launch 40-grainers at over 3900 fps. That’s bookin’. This makes the 20 Practical a great choice for an AR-based varmint rifle.

20 Practical20 Practical Ultimate Varminter
A decade ago, as a “proof-of-concept”, AccurateShooter.com created a 20 Practical AR15 Ultimate Varminter with a custom 20-caliber upper from Robert Whitley of AR-X Enterprises, LLC. That project rifle was ultra-accurate — every 5-shot group out of the gun was less than the size of a dime. That gun was auctioned off, but Robert Whitley continues to produce custom 20 Practical AR15 uppers. (The 20 Practical cartridge is simply the .223 Rem necked down to 20 caliber — you can use standard .223 brass and load with standard.223 Rem dies. Just swap in a smaller expander and use smaller neck bushings.)

Robert reports that the accuracy of the first 20 Practical AR15 was no fluke. After building six (6) more 20 Practical uppers, he tested them for accuracy and they all shot great. These uppers feature DPMS low-pro receivers with side charging handles. They are fitted with PacNor 1:11″ twist, three-groove stainless barrels.

20 Practical AR uppers

Robert reports: “We have been making more 20 Practical AR15 uppers and I have to say I am astounded by the accuracy of these things. For shooting little tiny groups out of an AR15 with bullets going 3500+ fps, it’s hard to beat the 20 Practical. Today I test-fired six more uppers, all with 11-twist barrels. Three of the uppers had 24″ barrels, two had 20″ barrels, and one had an 18″ barrel (we call it ‘Stubby’).

20 Practical Reamer print

In four of these uppers I shot re-sized Winchester brass using 25.3 grains of WC844 powder with Berger 40gr BTHP bullets loaded at 2.225″ OAL (about .015″ off the lands). WC844 is inexpensive military surplus powder that is nearly identical to H335. I tried three different primers and the choice did not seem to matter (CCI BR4, Rem 7 1/2s and Win Small Rifle — the old silver ones). All these four uppers shot great. Here is an animated GIF with targets from uppers #6, 10, and 11. All groups are mag-fed, 5-shot groups shot at 100 yards using a front rest and rear bag.”

Targets Shot with Three Different 20 Practical AR Uppers

20 Practical AR uppers

For more information visit www.6mmAR.com, or contact Robert Whitley via email: rcw3 [at] erols.com.

Permalink Bullets, Brass, Ammo, Gear Review, Gunsmithing No Comments »
January 20th, 2019

Amazing 1K Video: 10 Shots in 4.554″ at 1000 Yards (100-6X)

Scott Nix Dasher Record

6mm DasherHow well can the little 6mm Dasher perform at 1000 yards when the conditions are good, and the shooter is riding a hot streak? Well here’s a shot-by-shot record of Scott Nix’s 4.554″ ten-shot group shot at Missoula, Montana at the Northwest 1000-yard Championship a few years back. All 10 shots were centered for a 100-6X score. That’s about as good as it gets. If Scott had stopped after 5 shots, his group would have been under three inches.

Video Demonstrates Amazing 1000-Yard Accuracy
Watch the video. You can see the group form up, shot by shot. It’s pretty amazing. Scott’s first shot (at the 45-second mark of the video) was right in the X-Ring, and four of Scott’s first five shots were Xs. That’s drilling them! This video was recorded from the pits at the 1000-yard line, during record fire.

Permalink - Videos, Competition 4 Comments »