First sizing of 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 have read where 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

[bigdaddytacp]

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 have read where 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

................For accuracy loading the first resizing should be full length....this is to get the brass all to the same size.....same as uniforming the pp/flash holes and trimming....MOST/MANY people use the first firing as a FIREFORMING load.....load the round with a long seated bullet to force the case aganist the bolt face OR use the "cornmeal" fireforming load method.....then the case will be formed to YOUR chamber and will work with just necksizing for X number of loads according to your brass/chamber/dies and load........the full length sizing also makes it easier to measure the wall thickness to mark the thin/thick side and decide on neck clean-up/turning and makes the case fit the neck mandrel on the trimmer/turner that use them.......some brass needs the full length more than others and according to how the new brass matchs your chamber and the full length sizing removes any factory dents,misalignment of the body/neck and just lets you start with a "fixed point" with that batch-lot of brass...imo.....good luck and good shooting-loading!!!!

[KN]

If you have already fired them then full length sizing wont do you any good now. Like Bigdaddy said, It's really just to make sure all the brass is uniform and will chamber correctly the first time.  KN