Do you know anyone that actually neck turns brass for their AR15?  It is kind of unheard of actually.  After all, this is not a bolt gun in a National Match competition.  But who cares if its not done, we just want to know if it matters, and what impact it has?
Our method:
  1. K&M Neck turning equipment
  2. Redding Competition Full Length Sizing die with expander ball
  3. Neck tension is about 2 thousands
  4. Hornady Concentricity Tool, all bullets less than 2 thousands of runout (which means the bullet is not crooked in the neck of the bullet by more than 2k.  within 1K is perhaps idea, but a few pieces could not get better than 2k, most where 1k.
  5. Length of brass trimmed to 1.750
  6. Brass prepped
  7. Federal Gold Medal Small Rifle Primers
I don't really like the K&M kit, although its one of only a few options there is for .223.  The damn guide rod for the brass is like .001 too big, so you have to buy their expander and die adapter too, or you will gall the brass pretty bad.  So they sell like a $45 carbide guide rod piece that helps with galling.  What I don't like, is you can't buy a simply kit. They nickel and dime you a la cart for everything.  And the guide rod is too big, because I don't know one expander ball made that can make the brass large enough to work on guide rod.  Its .001 too big.  So you have to buy their expander? Why not just make the guide rod for the brass neck .2225? or .222?  What a giant hassle, it should be way simpler.  Too complicated.  Too expensive.  This all has nothing to do with its performance, it works just fine and good.  Once you get past the hassle of setting it up and all the time it takes, its a lot better.
Need sunglasses
Before we did this, we wondered what in the world would happen when we made brass literally "perfectly concentric and neck tension as close to perfect as you can get.  Wall thickness is nuts accurate consistent. 

We already shooting consistent near 1/2 groups in a few AR's, so is doing this going to make the groups better?  We didn't think that was going to be result at 100 yards.  But maybe...maybe SD and ES (Extreme Spread of Velocity) would improve because the neck tension was more consistent.

First of all, no matter what brass you get, the walls of the neck are not going to be consistent.  In this example, we shaved .002 off the neck, and as you can see, we need another .002  (2 thousands of an inch) to clean it up and make it consistent.   
Hornady Concentricity Tool  sells for about $150.  It measures bullet "run out" meaning how crooked the bullet is in the brass.  If you roll the bullet on a flat surface, you will notice bullets with run out, will wobble, the bullet will wobble.  Bullets that are very concentric and true aligned if you roll on a flat table, will not wobble, and roll very true and spin uniformly.

We tested 8 loads each
the 5/4 means the best 5 shots (5 shot groups) and the 4 is the best 4 shots out of 5.  So basically, since every AR15 does small flyers,  it removes the 1 flyer and shows you the accuracy of the main group. 

Initial impressions is that these loads are damn accurate?  But the non neck turned brass has "Larger" flyers.  I also made 2 mistakes and fired an extra shot on bottom target.  The bag rest shifted right when I pulled the trigger, I had new bags and they were too stiff.

If there is a better load for an AR15 than 21.5-21.7 Grains of Benchmark using a Berger 77 OTM at 2.255, we don't know about it.  OK, that was a joke, there are many great loads.  But this load is consistently great.
Data doesn't lie..
Rank 5 = all 5 shots counted in group size
Rank 4 = best 4/5 shots counted in group size
ES= Extreme Spread (Velocity range)

Neck turned correlations:   If you neck turn your brass you will probably get better SD and better ES.  How much better?  well in this case, SD was 28% better overall and ES was 31% better.  That is A LOT better.  If we take out 2 flyers which caused the non neck turned to average overall at .81, its basically very similar accuracy to neck turned, at 100 yards.  As you can see, the best 4 shot groups for both were under .5 inches, so we can conclude neck turning produces "less larger flyers".  Here are points about neck turning:
  • less impact from flyers
  • Better SD
  • Better ES
600 yard F Class?
We will make a dedicated F Class page.  But lets analyze these loads here, to see if it would be good in F Class

If one is to compete in 600 yard F Class, we can see from the illustration on the left, we would want a load with ES more more than about 15 If that was possible to build consistently.

This illustration represents "maximum impact" of ES.  That means that the ES is always, 100% LESS FPS, than the majority of your shots.  Like this example of ES 20.
2585  This one might hit about 2.5 inches BELOW the main group.  As represented by the PINK dot inside the 9 ring. 

The X ring is .5 MOA, or 3".  So if you can actually get a .5 MOA load that is consistent, and there is zero variable wind, and your ES is basically less than 5, you might be able to theoretically hit the X ring a lot.  But the X ring is worth same points as the 10 ring, all it does is break tie breakers.  So if you have 4 in X ring, and your competitor has 3 in X ring, and you both scored 197/200, then you win.

What is more likely to happen, in an ES spread of 30, is some loads will be +15 FPS above normal area, and some will be -15 FPS below normal area.  If this was the case, you would be RIGHT on the edge of the 9-10 rings with your +/- 15 FPS shots.

In the end, in this class.  Accuracy is most important, but speed also matters, and 2600 FPS would be on slower end of the competitors, almost guaranteed. As normal velocities in this field would range from say 2600-2800.  2800 is one and done brass...very hot. 
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