Question On Brass Neck Sizing Consistency

[Crackers]

Hi all,

Late Merry Christmas to you all and happy New year.

Question -

I have 100 Lapua 6.5-284 cases necked up for my brand new 284. I have fire formed all the brass using the same load on all brass in the same rifle.
I am neck sizing only using a Wilson neck die, and what I have noticed is that out of the 100 cases about 20 required very little pressure to neck size ( Very little visual clues on the neck.) While the rest required firm pressure, ( Nice visual band around neck from bushing.)

I am newish to reloading (12 Months) and I was wondering what would be a cause of this?

Cheers

Crackers

 

[Zia Hunter]

You may want to check the neck wall thickness of the cases. Are you expanding the necks when sizing?

 

[Crackers]

The only neck expansion was when it was sized up from 6.5 to 7mm, but since then, no. Just fire formed then neck sized only.

 

[Zia Hunter]

Then I would check neck wall thickness for consistency.

 

[357Mag]

Crackers -

Howdy !

After you check those neck walls, you'll probably end up wanting to outside neck turn.

Even an super minor outside skim trim will give evidence of any neck out-of-round; or lop-sided neck wall thickness.
One of the reasons why different NS bushing diameters are offered for the various calibres.

With regards,
357Mag

 

[Crackers]

Hi again,

As I am relatively inexperienced in the world of reloading, I am just trying to get my head around the process a bit.

With new brass when it is fired for the first time the fire forming to the chamber sizes still leaves some minor variances which you then pick up when outside neck turning?

Second question, when going to outside neck turn do I measure and take all the brass down to the thinest neck thickness for consistency.

Craig.

 

[Zia Hunter]

I typically include neck turning as a step when preparing new brass. Use an expander mandrel then turn on a tool such as the ones offered by Sinclair and others. If necks need to be turned after firing, there are two options; you can neck size then expand the necks to fit the turning mandrel or use a Forster neck turner which is designed to turn after sizing. I have both and prefer turning before firing.

The following link has a good article on case preparation that you may find helpful.

http://www.6mmbr.com/jgcaseprep.html

 

[Larryh128]

Whatever you do on neck turning, it needs to be consistant. I turn everything to .013 wall thicknes. Some cases will only be skimmed on one side & others will remove material on the whole diameter. You shouldn't see much variation on thickness with the Lapua brass. Some other brands are a lot more inconsistant in neck thickness.

 

[Hengehold]

Your questions are great and I wonder what your application will be for this ammo. If you are shooting prone with a sling or even new to F-class I will suggest that you not waste your time turning necks and spend the time perfecting your position and shot exicution. While it does improve neck tension consistency from one piece of brass to the next, Lapua is usually so consistent that turning brass is a little overboard for the above applications. If bench rest is your game then I suppose you may see some of the benefits downrange.

If you decide to neck size, you may want to consider the Neck dia of chamber. The greater the difference between your chamber neck dia and your case neck dia, the more you will be working the brass when you resize. The more you work the brass, the faster you will work harden the brass and have to throw it away because of splitting necks and erratic neck tension. 1.5-2.0 thousandths of clearance between brass and chamber is a safe place to
be.

Hope this of some help and best of luck.
Trevor

 

[expiper]

go one thou smaller on your sizing bushing...the one you are using is not quite small/tite enuff...the problem will go away when you give em enuff squeeze.....Roger

 

[Steve Blair]

Your questions are great and I wonder what your application will be for this ammo. If you are shooting prone with a sling or even new to F-class I will suggest that you not waste your time turning necks and spend the time perfecting your position and shot exicution. While it does improve neck tension consistency from one piece of brass to the next, Lapua is usually so consistent that turning brass is a little overboard for the above applications. If bench rest is your game then I suppose you may see some of the benefits downrange.

If you decide to neck size, you may want to consider the Neck dia of chamber. The greater the difference between your chamber neck dia and your case neck dia, the more you will be working the brass when you resize. The more you work the brass, the faster you will work harden the brass and have to throw it away because of splitting necks and erratic neck tension. 1.5-2.0 thousandths of clearance between brass and chamber is a safe place to
be.

Hope this of some help and best of luck.
Trevor

Trevor,

The OP is expanding 6.5-284 up to 7mm, an operation that introduces neck thickness variation, regardless the original neck. I use Lapua 6.5-284 brass for my .284 Shehane and find that neck thickness varies considerably after expanding. I turn all necks to .012" wall for a .313" chamber, allowing .004" diametral clearance. The larger calibers, 7mm and .308, seem to benefit from a little more clearance than the smaller ones, especially with long bullets. I do anneal the neck and shoulder every three firings to preserve ductility.

See you on the range in '12.

 

[Crackers]

Your questions are great and I wonder what your application will be for this ammo. If you are shooting prone with a sling or even new to Class I will suggest that you not waste your time turning necks and spend the time perfecting your position and shot exicution. While it does improve neck tension consistency from one piece of brass to the next, Lapua is usually so consistent that turning brass is a little overboard for the above applications. If bench rest is your game then I suppose you may see some of the benefits downrange.

If you decide to neck size, you may want to consider the Neck dia of chamber. The greater the difference between your chamber neck dia and your case neck dia, the more you will be working the brass when you resize. The more you work the brass, the faster you will work harden the brass and have to throw it away because of splitting necks and erratic neck tension. 1.5-2.0 thousandths of clearance between brass and chamber is a safe place to
be.

Hope this of some help and best of luck.
Trevor

I think you are right here Trevor. I have been shooting F Class here in Australia for just over 12 months and I think that better gains could be achieved thru time on the trigger. All the information everyone has posted here has certainly help me better understand a few issues that I will address when time comes to go that extra bit.

Many thanks to all.

Regards

Craig.