A handloading secret that dates as far back as the 1930s could significantly improve your rifle's accuracy with a simple adjustment of your sizing die.. The secret is partial neck-resizing, a technique pioneered by early wildcatters, but little remembered today.
How could such a simple thing affect accuracy to any degree? The answer lies in understanding the factors that affect the accuracy of modern sporting rifles. Firearms manufacturers and semi-custom shops now offer rifles capable of gilt-edge accuracy at a price well within reach of most shooters.
As the accuracy pie is sliced ever thinner, reloading precision moves beyond a matter of uniformity in powder charges, bullet weight, seating depth, and so on. It's also important to achieve concentric, or more accurate coaxial alignment of your rifle and ammunition components along the centerline of the bore.
With a factory chamber that conforms to SAAMI specifications and conventional factory loads or handloads, the chamber dimensions are several thousandths of an inch larger than the loaded cartridge. As a result, the cartridge lies on the bottom of the chamber--which places the bullet out of line with the bore. When the round is fired, the bullet enters the throat and engages the rifling at a slightly skewed angle, inducing a tiny accuracy-degrading wobble when the bullet leaves the bore.
The effect of such bullet wobble is fairly small--0.2 MOA or less in most cases. You probably won't notice it unless you shoot a rifle capable of sub minute-of-angle accuracy. Then, a 0.1 or 0.2 MOA improvement becomes pretty significant.
That's where partial neck-resizing comes in. With the neck resized some two thirds of its length to grip a seated bullet, the rear third remains expanded to provide a sliding fit with the chamber neck. When you chamber the loaded round, the still-expanded base of the cartridge neck bears against the neck area of the chamber, lifting the seated bullet into near-perfect alignment with the bore centerline as it enters the throat.
Adjusting your resizing die to partially resize cases isn't difficult. First, blacken a fired cartridge case by passing the neck and shoulder area through the flame of a candle. Then place the case in the shellholder of your loading press.
Back out your resizing die at least half an inch and loosen its locking ring. Next, lower the press handle, raising the blackened cartridge case to the top of the press stroke. Now, screw the resizing die into the press until you feel it rest firmly against the mouth of the case, then raise the press handle, retracting the cartridge case.
At this point, decide how much of the case neck you wish to resize and figure how far down you need to adjust the resizing die accordingly (on a 7/8 X 14 resizing die each full turn = .07 inches). Leave the adjustment a bit short for fine tuning.
Once again, lower and raise the press handle and check the blackened case neck. If you're not satisfied, adjust the resizing die up or down. When you have the die adjusted correctly, lower the press handle, reinserting the case into your resizing die. Now, adjust the locking ring and tighten its set screw. Finally, raise the press handle and remove the blackened case.
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