neck sizing

[Funky Bunch]

as I only neck size i was wondering exaclty how much of the neck do you really need to size ?? on my WSM I do the full neck length as the bullet need to be held quite tight under recoil when bullets are in the mag

but on my 243 I only used to sixe 3/4 and under closer inspetion I can get away with only sizing half the neck

has anyone done any experiments regarding this

[shootingbags]

as I only neck size i was wondering exaclty how much of the neck do you really need to size ?? on my WSM I do the full neck length as the bullet need to be held quite tight under recoil when bullets are in the mag

but on my 243 I only used to sixe 3/4 and under closer inspetion I can get away with only sizing half the neck

has anyone done any experiments regarding this

Funky,

 

I know some of the benchrest guys literally just size enough to grip the bullet. On both my 223 and 243 I have always done pretty much the full neck with excellent results.

[Guest varmartin]

The thinking behind sizing part of the neck is two fold. ( may be more advantages ? )

 

1. The unsized portion of the neck helps with concentricity, keeping the neck area centred in the chamber as close as possible.

only `spring back` of the case is the size difference.

 

2. It can give the doughnut some where to form ( without being a concern ) if case necks are being turned for a custom chamber size.

 

Martin

[Guest northernchris]

If you have a look at how much a Wilson sizing die sizes it about half the neck length.As has been said enough to hold the bullet,which is fine if you are single feeding,but if out of a mag i would have more neck tension just to cope with the recoil the rounds in the mag will see.

[craigyboy]

my wislon die sizes exactly 3/16 of the neck and the instructions with the dies claim all there dies only size the first 3/16 of the enck as its the preffered method of benchrest shooters. Its suits me as my rifle is single shot.

[Guest varmartin]

my wislon die sizes exactly 3/16 of the neck and the instructions with the dies claim all there dies only size the first 3/16 of the enck as its the preffered method of benchrest shooters. Its suits me as my rifle is single shot.

 

Craigyboy

 

Do you mean ...3/16 of 1 inch of the neck ( 4.76mm ) or ...3/16 of the neck length ??

 

Sorry if its a daft Q.

 

Martin

[6BR]

hi to all

 

when neck sizing you only need to size the length of the neck were the bullet is seated plus 10 thou. the unsized part of the neck keeps the case concentric with the centre line of the bore.plus your cases will last a bit longer as your not over sizing.

but if have a fast twist and use, long heavy, vld type bullets you may have to size all the neck as the base of the bullet goes past the shoulder/ neck junction.

[craigyboy]

Martin its 3 1/16 of an inch i.e 4.76mm.

[Guest varmartin]

Cheers fella, that`s what I thought you meant.

 

I size a bit more than that, but then I mostly shoot 95 Bergers outa my 6MM BR.

 

Martin

[silentsoulsleave308holes]

Bench rest shooters typically use smaller lighter weight bullets than say an f-class shooter as their concentration is getting the maximum accuracy at one set distance and for this they tend to use flat based bullets as these have proven themsevles at say 100yards to 300yards

 

Many that start the sport have been using rifles that are off the shelf and actually throated for a longer or higher bc bullet to begin with, thats right bench rest shooters dont shoot the higher bc bullets, check for yourselves.

 

Because the rifle was throated for heavier and longer bullets than the bench rest shooter uses it means to engage,sit touching or just near the lands the smaller bullet usually has its base somewhere up the neck of the case instead of inside the case as a heavier bullet would

 

Therefore it would only be necesary to size the portion of the neck that the bullet is actually using, as to size the rest is a waste of time

 

There is an advantage in doing this that I will mention in a mo

 

Assuming the chamber was cut precise to the bore, and you would have to check one of your cases that has been fired on a run out guage that reads 1/10 thou as a 1thou would not be good enough and if run out is less than a thou then it is worth you neck sizing only

 

If your chamber has a runout of more than a thou then you would be better full length sizing only as you only increase the problem by neck sizing

 

Example: I have a .243 stock remmy that has a chamber run out of 4thou to the bore,in theory, if you can imagine looking at your case and actually being able to see the neck of the case sat to one side of the case and you only sized the neck and seated a bullet, then the chances of you being able to insert the round in the exact orientation to match the run out is nearly impossible

 

The missalignment to the bore is greatly reduced if you full length sized, and this has been tested and proven to be true and in this case accuracy is better with full length sizing

 

Now back to the advantage I was talking about, lets say your chamber run out is good and lets remember that no chamber is 100%, there will always be a little run out.

 

The chamber is good so neck sizing only can be done and you want to shoot little lighter bullets for bench rest, so you have only need to size the part of the neck that the bullet is taking up,as these little buggers don't sit the full way in the case, then when you fire form the cases the unsized part of the neck will fireform to the throat part of your chamber that is cut from the bore and so greatly increases line up of your bullet to bore, so you can see the advantages there

 

There really ain't any advantage in sizing only part of your neck for long bullets that would sit the full length of the neck anyway, only disadvantages

 

 

 

silent

[Vermincinerator]

Hi Silent,

Great description buddy but users of Wilson hand dies have no choice but to size only a portion of the neck as there is no adjustment.

I have used bullets seated passed the sized portion and also boat tails in my 6mmBR and have not noticed any difference in accuracy compared to bullets seated shallow.

 

Ian.

[silentsoulsleave308holes]

I just tried to give both sides of the story as to theory etc

 

at the end of the day what counts is what works for your gun and many hear different stories or theories with out knowing the full back ground of why or where they came from so I just tried to make it so people who may have questions got them answered.....I hope?????????????

 

many hear about part necking etc etc etc from bench rest shooters and try to duplicate not actually knowing why they are doing it.... I know, been there myself as I am sure most have

 

Over the last five years, well actually the first four of the last five years, all I have been doing is testing etc etc and try to share my end results, and it was interesting to find that others who have been testing the same theories have had the same results

 

I hope it will help in some way

[craigyboy]

Silentsouls I know exactly where you are coming from, in my cooper rifle in .204 ruger chamber runout was a dissapointing 9 thou (the chamber was very very poor) I tried neck sizing only and a round simply would not chamber unless I orientated them the way they had been originally fired I had the rifle rebarrled by Neil Mckillop and fired case run out is less than 1 thou and neck sizing only is not a problem, rounds chamber spot on, my original .204 ruger chamber is at the very extreme end of a poor chamber but it shows what effect runout has in a chamber.