For those who seek maximum accuracy from their rifle reloads turning your brass case necks is worth considering.  The eccentricity of neck brass is shown in the drawing below as an exaggeration, most cases have just one or two thousandths of an inch variance. 

So, what’s the big deal here anyway you may ask.   The answer is if the neck is out us of round it will cause the bullet to be out of alignment with the center of the bore.  This will cause the bullet to move perpendicularly to the bore axis slightly when fired.  In other words, the bullet will take a slight S curve path from the case to the rifle bore.  Although this is very slight it is not conducive to optimum accuracy.  When everything is lined up exactly on bore axis this is one step in attaining the best groups possible. 

There are quite a few neck turning tools on the market today.  One favored is the Sinclair International model 4000 premium neck turning tool.  I have used this tool in the past as well as one of their competitors and found the Sinclair superior as it is easily adjustable in .0002” increments.  A shop metal turning lathe can also be successfully used by making a custom mandrel that fits the inside of your case neck.  Using either method a little sizing die wax on the mandrel every 3 or 4 cases will be helpful. 

There is one area you must be precise when turning necks.  If neck turning is stopped slightly short of the case shoulder, then you have two different neck diameters with a small larger ring on the outside of the case adjacent the shoulder.  If this is present, upon first firing this DREADED RING will transfer to the inside of the case when fired the first time.  To avoid this problem when turning the neck as the cutter approaches the shoulder wait until the brass chip comes off very slightly larger then immediately stop advancing and let the cutter complete at least one revolution to have everything equal.  This is a very precise operation and if you do not have good eyesight and patience then neck turning may not be in your wheelhouse.  Of course, once neck turning is completed on a lot of brass it never has to be repeated.  We hope this has been helpful in your quest for accuracy. 

Tom Wilson                                                                                         © Fort Smith, AR 5-27-24 

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