Now I know that 15 rounds does not a statistical certainty make, but it’s enough to give you a good indication if something’s working. For each batch I fired two fouling shots and then followed with three record groups. Then I cleaned the gun and allowed it to cool to ambient temperature before firing the next batch.

My range is known for unpredictable winds, so I have wind flags up, and for this particular test I waited for one of those nice rare days where winds were very light and steady. All loads are new Winchester brass using Remington small rifle benchrest primers and charged with 24.0 grains of Alliant 10-X with a Hornady 52 grain A-max bullet. Overall length is 1.889 inches. The results are shown in the accompanying table.

Before we even look at the accuracy, pay some attention to the extreme spread and standard deviation. Those numbers represent all the shots fired under each neck condition. Conventional wisdom seems to hold that you must have a small standard deviation to get good accuracy, but time and again I’ve seen that simply to be untrue. Sure it’s nice to have one, but that in no way promises better accuracy.

The accuracy results show the typical influence of the bell curve, but the averages give a strong indication that variations in neck thickness make a difference. And the appealing thing is that this is a quick and dirty sorting procedure. I didn’t do any of the other case prep stuff to primer pockets and flash holes. All I did was sort by variation in neck thickness.

Obviously we will find differences in other makes of brass, and my choice of Winchester was driven by the fact that it is readily available and reasonably priced. The other good news is that the Redding gauge doesn’t require much work on our part and doesn’t cost a bunch--retail is $96.

The main thing, at least for me, is that it is clear to see the benefit for the effort involved. I surely won’t do it for every cartridge I load, but for my varmint and tactical rifles where accuracy is a major concern it can easily become part of the routine.

EFFECTS OF CASE NECK VARIATION
Neck Variation (in.)	Muzzle Velocity (fps)	Extreme Spread (fps)	Standard Deviation	Group 1 Size (in.)	Group 2 Size (in.)	Group 3 Size (in.)	Avg. Group (in.)
<0.001	3,358	114	29	.457	.243	.550	.417
0.0015	3,351	73	24	.514	.652	.493	.553
>0.002	3,353	54	16	.628	.768	.674	.690
Groups are five shots 100 yd. from benchrest. Velocity is the average of 15 shots measured at 15 feet with a PACT chronograph.