The main goal for most reloaders is to make the most
accurate handloads possible; something that has been discussed extensively on
our site. This often leads shooters to see how other shooters are reloading
brass. After all, what better way to learn, and not make the same mistakes, as
watching a veteran do it. One question for reloaders is deciding whether to
Neck Size (NK) or Full Length (FL) resize their cases. I used to neck size but
I now prefer to FL resize all rifle calibers. Most benchrest shooters today use
FL dies, because when full length resizing is done accurately, there are little
to no advantages to neck sizing.
Neck sizing used to be popular among target and varmint
shooters because it reduced chamber clearance and that extends case life by not
over-working the brass. Many shooters also figured that the tighter their loads
fit the chamber, the more accurate they'll shoot. There's more to this story.
Shooters that neck size eventually need to bump their case shoulder back to
ensure that their rounds will chamber reliably. Keep in mind that .001" is
one third the thickness of a human hair, and having some clearance is an
Reloading equipment (and techniques) evolve as technology
improves. Today, most benchrest shooters use expensive custom FL resizing dies
made specifically for their chamber. This allows them to make handloads that
ALWAYS fit perfectly. Yet, most reloaders can’t spend that kind of money on a
set of custom dies, and actually it’s not necessary.
Shooters that neck size know that their handloads will soon
require a bit more force to close the bolt, and that's not good. You should
NEVER be able to "feel" handloads chamber - not even a little bit.
Neck sized cases have absolutely no chamber clearance at the shoulder. When
they get tight, that shows they are obviously not consistently being returned
to the same size. Another consideration for our handloads is to make them with
near zero case run-out. However, after "forcing" a tight round into
the chamber, it becomes anything but concentric. Why would you want to
occasionally bump the shoulder just to make some cases fit better?
On the other hand, full length resizing must be done
accurately if it's going to make better handloads. It's best to bump the shoulder -.001"
to -.002" at the most. This
requires measuring the clearance (at the shoulder) that YOUR handloads have in
YOUR particular chamber. This is very easy to measure.
A properly used FL die bumps the shoulder, sizes the neck, and
slightly resizes the "tapered" body while your case is fully
supported; perfectly concentric in one die. When full length resizing is done
properly, it delivers the very best accuracy, improved case life, and reliable
chambering. How can you resize accurately with an ordinary full length resizing
Actual case measurements alone are worthless unless you can
also measure your particular chamber at the shoulder. Accurate full length
resizing means having - .001” to - .002” clearance at the shoulder (and no
more). This requires "measuring" the clearance that YOUR handloads
have in YOUR particular rifle. Then you
can set your FL resizing die to "accurately" bump your case shoulder
just like expensive custom benchrest dies. Your FL die can also resize the neck
while the case is completely supported (and aligned) inside one die, and in one
operation. Case run-out is reduced, accuracy is improved, and your handloads
will always chamber with a perfect fit.
Saving a fired case is like having a perfect casting of your
chamber. Just zero the gauge on the shoulder of your fired case. That
calibrates the gauge to YOUR rifle. Next, replace your fired case with the
first case when you begin resizing. The gauge then displays the exact clearance
(at the shoulder) that this case will have in your particular chamber. Then
you'll know how much to raise or lower your Full Length resizing die to make
perfect fitting handloads.