Reloading Accurate Rifle Ammo: Neck vs Full Length Sizing

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Reloading Accurate Rifle Ammo: Neck vs Full Length Sizing

Post by Zeliard »

Originally posted by carteach0.

Reloading Accurate Rifle Ammo: Neck vs Full Length Sizing

Hand loaders have so many choices, so many things to keep them up at night,
I thought I’d add some fuel to the fire.

Let’s look at yet another factor in loading accurate rifle ammunition, the method
chosen to size the case.

Usually one of two avenues is open to us; Full length sizing and neck sizing.

Full length sizing is just what it sounds like: The case is ‘resized’ along its entire
length. The die can be adjusted to change the depth of this sizing, or how far down
the neck and body the case is pushed into the die body.

Neck sizing involves just working on the case neck, leaving the body as fired.
This alternative has several side roads of its own.

Why is one type of sizing preferable to the other? Here opinions abound, but lets
look at a few of the major points.

Full length sizing assures the case will meet specification, and fit in almost
any chamber of that caliber that also meets specification. This means ammunition
feed and function should be reasonably trouble free. A shooter using his rifle for hunting,
some competitions, and defensive uses must consider this factor of utmost importance.
In addition, many semi-auto rifles do not function well with cases right at chamber size.

Neck sizing has the advantage of leaving the fired case expanded to match the chamber
of the rifle it was fired in. This closer fit promotes accuracy, pure and simple.
Neck sizing also works the case less, promoting brass life. As icing on the cake and
unlike full length sized cases, neck sizing requires minimal lube. That means one less
mess to clean up. Even with these advantages, cases fired with full power loads
often must be full length sized every third or fourth loading to preserve function.
Bolt action and single shot rifles are best suited to take advantage of neck sized cases.

There are several types of full length sizing. Most commonly encountered
are standard sizing and small base sizing. Small base dies take the base of
cartridge back down to minimum dimensions, and are usually reserved for
ammunition used in semi auto rifles with tight chambers. These creatures
can be found at national match ranges, with highly experienced shooters hovering
over them like a momma bear with a cub.

Neck sizing boils down to two basic types as well: standard and collet sizing.
Standard neck sizers squeeze the case neck into proper dimension, while leaving
the case body as fired. They first smoosh the neck into a tight hole that makes
it smaller, then drags it back over an inside neck sizer that opens it back up to
final dimension.

Collet neck sizing inserts a final dimension form into the neck then uses a collet
to squeeze the neck onto the mandrel. The brass is worked only once, and it’s not
pushed around at all.

In order to better understand and picture the differences between full length and
neck sizing, lets look at a pair of cases done one in each method.

For our purposes I chose a LEE die set containing both types of die in 8x57mm.


The collet neck sizing die, once disassembled, reveals the mandrel and neck collet
along with the tapered sleeve that squeezes it around the case neck.


A standard neck sizing die, and even a full length die, is quite easy to set up
and use. It’s fairly intuitive and the results can be seen and felt as soon as the
case is inserted and removed. The collet type die is more complicated, and
the builders directions should be followed closely. A mistake here can snap
the collet and destroy the die. Trust me on this..... I know this to be true.... sigh.

The standard sizing die is much simpler in design. The body of the die is
very closely machined to final case dimension, and the decapping stem contains
an inside sizing button that expands the case neck to final dimension as the case
is removed from the die.


In full length sizing, the case must be lubed over it’s entire outside, and a bit of lube
on it’s inside neck as well. I use a lube pad when doing just a few cases, and a spray
lube when doing a larger batch.


When neck sizing, full lubing is not required. Only a tiny bit of lube on the inside and
outside of the neck is sufficient. For this, I push the case mouth against the lube pad
and give it a slight twist. That’s all the lube needed!


I struggled finding a way to visually demonstrate the actual results of sizing.
Holding the cases in hand, the end product is obvious. Trying to make it clear
in photographs was a different matter completely.

I hit upon the idea of ‘smoking’ the cases. This involves an open flame from a
match or a candle played across the object, leaving a very thin coat of black
carbon behind.


Smoking the fully lubed case proved to be an obnoxious task, as the oil simply
did not wish to take on the carbon. The dry case application was a snap.
This is an old time way of marking up a part for fitting, and leaves a contact map easily
viewed, and measured if need be.


Running each case properly into its particular die according to the manufacturers
directions, we are left with two cases marked up to clearly show the difference
between full length and neck sizing.


The difference in the neck treatment is clear. The full length die forces
the case neck into a hardened steel hole, while the collet die squeezes the neck
against a mandrel with out over working the brass.


The kind of sizing chosen by the handloader is just that..... a choice. Most folks
are quite happy to stick with full length sizing, or ‘mostly’ full length sizing
accomplished by backing off the die a bit. Experienced loaders searching for
maximum accuracy often rely on neck sizing as one step of their process.

People loading one caliber for several rifles must either full length size or
dedicate one batch of cases to each rifle, if neck sizing for accuracy is the
method used., Neck sized cases don’t usually work well unless used in the
same rifle each time.

Consider it just another tool in the *large* tool box available to hand loaders.
Proud alumni of Transylvanian Polygnostic University. "Know enough to be afraid."

"Vertroue in God en die Mauser".-Faith in God and the Mauser.

"Send lawyers, guns and money." -Warren Zevon

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Re: Reloading Accurate Rifle Ammo: Neck vs Full Length Sizing

Post by DaleH »

Am very surprised you didn't mention that typically neck sizing is best used on bolt guns and full-length sizing is typically needed on gas guns ...

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Re: Reloading Accurate Rifle Ammo: Neck vs Full Length Sizing

Post by Smokey »

On the K31, neck sizing results in a case firmly stuck in the chamber on the second or third firing with full powered loads.
Loads should either be kept in the low 30 thousand psi range maximum; or alternated with very mild loads.
Arguing with someone who denounces reason is like administering medicine to a corpse.

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Re: Reloading Accurate Rifle Ammo: Neck vs Full Length Sizing

Post by 72 usmc »

Thanks for reposting this. It is one of the great old stickies. :dance: :dance:
To old to fight and to old to run, a Jar head will just shoot and be done with you.

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