Full Length Resizing vs
The main goal for most reloaders is to make the most
accurate handloads possible, and that often leads shooters to see how benchrest shooters are reloading. After all, nobody gets better
accuracy than a good benchrest shooter. One question for reloaders is deciding whether to Neck Size (NK) or Full Length (FL) resize their
cases. I used to neck size (decades ago), 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 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 advantage.
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. Most shooters don’t want to 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.
So . . . . how can you resize accurately with an ordinary full length resizing die?
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.
(That's why I developed our Digital Headspace Gauge.)
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. Our 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.