Monday, July 21, 2008

Neck sizing Vs. Full length sizing rifle cases.

(Note: This is a mostly a repost, done since it seems proper at this point)


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.

Normal reloading die sets come with regular resizing dies. These will roughly size the entire case to nominal dimensions and squeeze the neck tight enough to grip a bullet again. Such dies require the cases to be lubricated along their entire length, another step in the loading process. This lube must be cleaned off before the ammunition can be used.

One downside to full length sizing of rifle cartridges is the life span of the case. The more brass is worked, the more brittle it becomes. This leads to cracks and case failures. Another consideration... Cases fired and then fully resized tend to 'grow' in length, requiring trimming more often.

On the upside, full length sized cases tend to function very smoothly and chamber easily, an important consideration.

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, we'll 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.

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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.

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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 de-capping stem contains an inside sizing button that expands the case neck to final dimension as the case is removed from the die.

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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.

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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!

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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.

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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.

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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.

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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.

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The kind of sizing chosen by the hand loader 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.


16 comments:

LittleJoe said...

Hmmm... I've been gone on vacation for a week and it's just my luck that you would choose that time to write a very professional and informative series on reloading.

From what I have read so far we have a lot in common when it comes to reloading.

I prefer to full length size everything except my ammo for one particular gun and I always neck size it.

It's a custom built left handed, bolt action rifle with a .458 Wildcat chamber. I buy factory .458 Winchester Magnum ammo and shoot it off the bench to fire form the brass. From then on I neck size only and load the ammo for .458 Lott or .458 Ackley.

I generally only keep about 50 rounds each (Winchester, Lott, Ackley) around. This was my Safari gun when I hunted and went to Africa. One or two well placed rounds will drop the mightiest beast stone dead in its tracks.

I generally don't shoot more than 20 rounds off the bench. Even with a muzzle brake and a good recoil pad, this bad boy will give you a headache that lasts a couple of days.

Enough from me. You've pretty much covered it all here and did a darn good job of it too. My compliments to you on a well written series about reloading.

Molon Labe,
Joe

Weetabix said...

How many firings will you get out of a full-length sized case vs. a neck-sized?

Carteach0 said...

That is dependent on many factors.
How hot is the load, type of sizing, dimensions of the chamber, and more.
With the load in this series of articles, cases full sized every third firing and otherwise neck sized, and trimmed every few firings.... I am on their eighth time being loaded.

That may be exceptional, and I am planning on replacing the set of cases and doing it all over again this winter.

Rule of thumb... full power loads with full sized cases, can expect four or five reloads per case. More with neck sizing and even slightly reduced loads.

Now my straight sided pistol ammunition.... thats unlimited till they crack or get enlarged primer pockets. I have some .45acp cases that must have been loaded 20 times already.

og said...

Great, great post.

I have an Arisaka that was chambered to 30-06. Anyone who has one of these knows, the damned things are great rifles. But rechambering them leaves the back of the chamber too large for the '06 round. So when you shoot it the case expands just a bit in the back. Not dangerous, but bloody hard to full length resize. So I have 250 rounds of Arisaka-only 30-06. I neck size and trim to length only, and they work just fine. Other thing is, the Arisaka is 311 in diameter, so a 303 round shoots fine in it, hence the neck sizing die I use is a 303 British. Thanks for posting this. Reminds me I ought to load some up.

Mario_V said...

You forgot to mention the third method of neck sizing: bushing dies.

In addition to most common dies with expander ball, and a collet-type neck sizing dies, there are also bushing dies.

Unlike collet and expander dies, they size the neck from outside to the exact same outside diameter (unlike collet and normal dies that ensure inside diameter is always the same). In my experience, they are the easiest to use. You do need a correct bushing for your brass. In 30-06 I typically use .336 for lapua brass and .332 for remington and winchester.

Anonymous said...

thanks alot just did my first reload ever today and was wondering what the difference was. this was perfect information for me

Anonymous said...

Thanks for a great and very well written informative article!

New to rifle ammunition reloading, I wondered what was the difference which you so nicely covered both with text and pictures!

Again, very well done.

hondolane said...

I would like to know if it is advisable to neck-size for an AR type semi-auto rifle. In my case an Armalite AR10T in .308. Slam fires are my main concern as well as feed and function. I intend to dedicate a batch of brass for this rifle. Also if neck-sizing is not advised can I back a full-length sizing die off a little to achieve a little of the same result?

Carteach0 said...

Hondolane,

All the loading I have done for the AR family of rifles involved full length sizing. Both my Colt Match rifle and my AR-180b require a full length sizing to maintain function. Neither would happily feed anything else.

Could you neck size their cases? My advice is not to, and that holds on any autoloader. Slam fires might be an issue, as are feeding problems, stuck cases, and poor extraction.

The Car Doctor said...

Very informative article. I've be reading and watching youtube videos where people will buy a headspace gauge, measure their chambers and then adjust their FL sizing dies so that their re-sized brass matches the gauge(or slightly smaller). My question is what would be the difference between this method and simply using a neck sizing die?

Carteach said...

Car Doctor,

The difference is in the sizing method. With a full length die, even backed off a ways, the case body is going to be sized somewhat. With a neck sizing die, only the neck is sized, leaving the case as fireformed to the chamber of the last rifle it was fired in.

Both methods (and the one you mention as well) have their place in hand loading.

Mario_V said...

Car Doctor,

After neck sizing a few times, the case extends enough that you can no longer close the bolt.

The reason for backing off a full size die is to prevent pushing the shoulder back too much, but just enough, hence to have the longest possible headspace that will fit. This is supposed to improve accuracy.

Personally, I don't do it, as I noticed no accuracy improvement in my rifle (not even with neck sizing, to be honest). If I full size, I full size completely until the shellholder contacts the die.

Belette Sauvage said...

Thank's a lot for this article, very, very interesting.
Regards

Belette Sauvage said...

Thank's a lot for this article, it's very hepful and interesting. A pleasur to read.
Regards

clay said...

New to rifle reloading here. Can you take a once-fired case and adjust your FL sizing die to seat firmly against it as a compomise between the two methods?

Carteach said...

Clay,

Not really. One can set the FL sizing die to size about 80% of the neck, and that will suit as long as the handload is fired in the same rifle again. This may be better than total full length sizing (what you described) for accuracy considerations in a bolt action rifle.

There really is no substitute for neck sizing, if the rifle is suited to it.

That's not to say that full length sizing, or even 80% sizing can't be quite accurate in it's own right.