is it necessary to size new unprimed brass?

[bluto67]

as the title states, is it necessary to size new unprimed brass? i picked up some new IMI 7.62x39 brass a few weeks back at a gun show and now that i got my dies i was going to prime the cases so they'll be ready when i pick up the powder. since i use a hand held primer seater i wondered if i should size them first. quess i'm just being lazy and trying to save a step. would like to hear what thoughts others have on this matter.

 

[42769vette]

as the title states, is it necessary to size new unprimed brass? i picked up some new IMI 7.62x39 brass a few weeks back at a gun show and now that i got my dies i was going to prime the cases so they'll be ready when i pick up the powder. since i use a hand held primer seater i wondered if i should size them first. quess i'm just being lazy and trying to save a step. would like to hear what thoughts others have on this matter.

for the most accuracy yes i size unfired cases, for safe plinking ammo no i do not size new cases

 

[bluto67]

the rifle i'm loading for is a 7.62x39 AR with a 18" stainless barrel and an Adams Arms Gas Piston conversion. i use cheap tula/wolf russian stuff for plinking ammo. the reasons i wanna start a load for this is accuracy and proper function. i had to put a Wolff light recoil spring and a carbine piston in to get the action to cycle completely. Adams said the conversion wasn't designed for 7.62x39 and it doesn't generate enough pressure. They suggested the mods i did or opening up the gas hole in the barrell (no way). i plan on using AA1680 powder (with Hornadys 123gr. V-max bullet) as it had the highest pressures listed in my reloading manual. the rifle is accurate but maybe i can tighten up my groups with these loads.

 

[red_zr24x4]

I would size it

 

[Broom_jm]

For a bolt-action or single-shot rifle, all you usually need to do is size the neck to ensure it is concentric. For AR's it's probably a lot smarter to FL size, so you know they'll chamber. Let us know which way you go and what your results are. I'm not sure if you're dead set on the powder or not, but RL7 is also an excellent choice.

This is an interesting project and I, for one, would very much like to hear more about it. Come back and share, if you get time.

 

[parson]

I always do. Don't know that it's necessary, but I'm old, and it's hard to change.

 

[sloughfoot]

I neck size. I don't full length size new brass. Too many times I see dented or oval necks in new brass. I have never had a problem with shoulders, just the necks.

It can't hurt to FL size, but since the shoulder is always too far back already in new brass, little is accomplished.

 

[bluto67]

well i decided to full length size the brass, don't have a neck sizer die. i did see a few cases where the necks were dented. i went this afternoon before work to Four Guns to pick up some powder. they were out of AA1680 but had RL7 so that'll be my test powder. the RL7 was $3 cheaper too. thanks for the responses, i plan on loading up some rounds here maybe tonight or tomorrow after work, then hit the range and bake in the sun. i'll keep you guys updated. thanks again.

 

[lon]

Like others have said, no need to full length size brass that is already at minimum spec. just to round out the mouth.

For the few pieces with dented mouths, I'll take a round rod, like the striking end of a manual decapping rod, and gently bend them close to round. Its not hard to get them round enough to seat a boat-tail bullet.

Now that you have nice, round case necks you should go ahead and very lightly chamfer the inside of the necks so the bullets seat nicely without shaving copper.

You can neck size with a full-length die by just raising it a little from contact with the shell holder.

 

[Broom_jm]

As Ion indicated, you can use a FL die to make the neck concentric by either backing it out significantly, or you can just "short-stroke" the handle on the press. You'll feel it doing the job well before actually sizing the case body and that's all you really need.

Good luck on the actual loads and please let us know how they shoot.

 

[wsenefeld]

Check and see how the bullet sits in the new brass. Some people have had problems when they didn't size new brass, the bullet would fall into the case and sit on top of the powder.