Should I full length size my new brass....

[jonr]

Hey everyone. I have a question. I am hand loading for my .308 using new Winchester brass. These loads are for target shooting. I have been just neck sizing the new brass with the Lee neck die. My accuracy has been good so far. 5/8" at 100 yrds.

My question is should I be full lenght sizing this brass before the first firing and then neck sizing after that? Why or why not concerning the initial full length sizing?

I just want to under stand the principles involved here. I under stand the reason for neck sizing, but not the reason for full lenght sizing before the first firing.

The reason I am ask is b/c I read where that others were using this approach.

I have noticed that my brass has shrunk in length about .004 after the first firing. It is no where near the need to trim length. It is about .015 short of it.

If I should have full lenght sized the brass before the first firing should I back up and full lenght size it now that it has been fired or just neck size untill full lenght is nessicary?

Thanks!

Jonr

[Jose Grande]

As long as you are shooting it in the same rifle, neck sizing is all you need. Full-lenght is for when you don't know which gun might get a particular round of ammo.

[longwinters]

My understanding is to full length size new brass and then neck size only (for target rounds) after that.  Some say that for hunting rounds you should always full length size for each loading.  I only neck size after initial firing and have never had a problem.  

long

[Agent_Smith]

It sounds as though you may have a larger body in the chamber and possibly a little more than normal headspace if the cartridge OAL is shrinking upon firing the first time. This is not at all unusual for a factory chamber made on new tooling (dimensions shrink after the tooling wears and dimensions get tighter generally).

Full length size the case initially to try and maintain some degree of straightness and concentricity. After the first firing you can put a fired shell (well lubed) into your shell holder while leaving the die loose and the die base about .100" off the shell holder. Run the case up into the die (minus the decapping rod) to the full stroke of the ram and leave it in the die while tightening down the die lock ring. This fired case SHOULD be concentric after coming out of your chamber and will align your die in the press, while taking the backlash out of the die/press threads.

In effect what you have now done is to align your die and set your neck sizing very marginally while maintaing zero headspace and barely touching the body. Your brass life should be as good as it gets under this scenario. Picture this as well...you will create a shoulder or bulge at the base of the neck (that .100" dimension) that exactly matches that of the chamber. You simply cannot get better axial alignment of the bullet relative to the bore under this circumstance.

I use this sizing method if I'm faced with a large chamber such as yours. Accuracy is generally quite good using this method.