New brass chambers... just load and go?

[megastink]

I bought some virgin Norma 7mm Rem Mag brass. It chambers in my rifle no problem. Length is 2.494", right in spec. Can I load it and go, or should I resize it? Should I size just the neck?

 

[CodyMac746]

I at least size the necks, just to ensure they are round. Sometimes they get bent/dented from shipping

 

[Pdyson]

I always run em through just to be sure. Often the bagged brass has dented case mouths, the expander button will iron them back out.

 

[Beluebow]

Expander mandrel/ball...lube the necks and load.

 

[RegionRat]

Sizing the shoulder/body is an option and may or may not change anything depending on your dies and how the OEM sized the new brass.

Sizing the neck is definitely a good plan.

A mandrel at the very least acts like a gage pin to show you how these sit relative to what your best brass prep should be, as well as correcting any shipping damage. If your mandrel slides in too loose or too tight, you then have the opportunity to correct the neck sizing.

I also apply the chamfer I want to brand new necks, and then monitor the seating force.

If you are getting picky, it is good to understand how to use virgin brass versus your fired brass without wasting the first cycle.

The best outcome for us is when virgin and cycled brass shoot to the same DOPE, but when they do not I find a way to make it so.

 

[Taylorbok]

I also run a mandrel into the neck then chamfer/debur.
If you don't use mandrels the sizing ball on your sizing die works just fine

 

[Rosebud]

If you can get a lee neck size die just run them through. No lube needed.

 

[qmrp2567]

I always run them through FL. I also do all the primer side case prep: Chamfer the flash hole to take out the burr inside the case. I have alos seen some new brass with off center flash hole.

 

[Mikecr]

Unless I need to form a false shoulder, to headspace off, I don't size new cases before firing.
My chamber is my best die. That's where perfect sizing occurs.

 

[Varmint Hunter]

Today, I run new brass through a FL die just to round out necks. But for many years I just loaded and fired without a single issue. Even if necks were slightly out-of-round, seating the bullet took care of the problem.

Sometimes I think we over-think things.

 

[Taylorbok]

Today, I run new brass through a FL die just to round out necks. But for many years I just loaded and fired without a single issue. Even if necks were slightly out-of-round, seating the bullet took care of the problem.

Sometimes I think we over-think things.

You can usually seat bullets in new brass without issue but it can and will affect your neck tension which can affect accuracy. for the couple minutes it takes to run an expander its worth it.

 

[qmrp2567]

Neck tension issues is actually what I see the most. Not a big deal if you want to just fire form into a particular chamber. I use cast bullets for this purpose. The a slight oversize on cast diameter usually takes care of it. I don't expect great accuracy, almost 90% the groups are excellent.

 

[Mikecr]

Sometimes I think we over-think things.

I agree, except IMO it's more under-thinking of things, before over-acting.
It seems often that folks take wrong actions, merely for the sake of 'consistency',, only to cause inconsistencies.
And they don't know it.

The only sizing we will ever do to actually make brass consistent -is fire forming.
Your brass is never more consistent than as pulled smoking from a chamber.
So any downsizing we do after that, necessary or not, a lot or a little, degrades consistency.
A way to manage this is to use custom sizing dies, fitted from YOUR fully fire formed cases (the best standard).

New brass is very inconsistent, and downsizing of it only serves to amplify this condition.
When you downsize, you roll brass thickness, hardening it here & there. You can think of it as adding energy, or adding character.
When you downsize inconsistently, because the brass you're sizing is inconsistent, you amplify different character in each case.
You have no way to remove the abstract energies that you just added, except to anneal. But you can't anneal away as much as you added with FL sizing.

So if FL sizing is in your plan, then your objective should be to add all that energy consistently across your batch of brass.
That occurs only with fully fire formed cases.
If you FL size before or during fire forming, then you will never reach stable dimensions. Your brass will endure perpetual change for as long as it lasts.

I realize this matters not to most folks. But with a question of whether you should size before fire forming, I say you should not, unless you have to. And it won't hurt anything to wait a bit on big sizing, until it's needed.
There is an approach that includes pre-work hardening of web areas, where that's the only way to make brass last. Cool plan, but I would use a custom ring die for that. Not a FL die.