I am just learning to reload, so my question may sound silly.
I just bought some new unprimed brass. I assume these should be re-sized just like used brass?
Thanks for your input. Any recommendation is most welcome.

Hi, WSAR15:
If they're bagged, resize them. They get bashed around enough in shipping that it pays. All you need it one that gets wrecked when you try to seat a bullet, or one that won't chamber, to spoil your day. Boxed cases might be OK. By boxed I mean shipped in ammo style boxes that keep them separate. Been there, done that.

Bye
Jack

I resize all new brass. Especially rifle brass. Always... ==Bob

Better to size them....not all new cases have been "babied", even if you got them in compartmentalized boxes, they probably spent a good bit of time rattling around as bulk before being boxed. The object is to be able to duplicate your reloads...better to size the new cases so you start out with the tolerances you'll have on every other reload.
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Goiod to give them a visual inspection even as brand new brass...someplace on the bench is a case that never got a flash hole, several that have well off-center flash holes, and one without a rim...all new cases.

I re-size. They're 458 Socom. Thanks!

WSAR15,
I usually only neck size new cases. With a straight wall case, that would entail only sizing the portion that the bullet is actually seated in. With a bottleneck it's pretty self explanatory.

I usually neck size new cases too. Sometimes deburr them too if I think they need it. Fred

In agreement with Fred,
I do an inside and outside chamfer of every case I load no matter if it is new or fired, progressivley loaded pistol rounds as the exception. If the new cases are to be crimped into a cannelure or crimp groove, I trim them to a uniform length before they have ever been fired. Most anything that punishes me from the bench will have full case prep before it ever is in the chamber. That would include a neck size, primer pocket deburring, primer pocket depth uniforming, and a trim to length with a outside and inside neck deburring. It's good to get rid of the "variables" before you subject yourself to a pounding in the quest for a good shooting load.

I don't weigh cases, even though I have a digital scale, I feel it is a blatant waste of time. I check a handful of necks sized cases for runout to verify I have a good die set. I also check all rounds for bullet runout if I suspect I have a die set that is not as it should be.

I use Redding dies for almost everyting new I try. I won't say I've never had a concentricity problem with them, but it's been far better than average of the brands available. Aside from one problem, which was corrected immediatley with no charge right down to the shipping, I'd have to say that Redding dies are my preference.

I usually size, deburr the flash holes on the inside, ream the flash holes(.081 drill) uniform the depth of the primer pockets, (a tool that is easily bought). I am also of advocate of the minimum length case, so I usually trim my cases a little on the short side, especially the ones that are for leverguns that need a crimp to hold the bullet in place. They tend to be a little more accurate this way. The plus side of all this is you are doing this work on cases that are clean, and you will learn just how uniform your brand of cases( this I advocate also, one brand of cases, no mixing) are from the factory. I have on occasion, gotten .357s that had such an undersized flash hole I had to drill it before I could trim it. These are just some of the things I do to make, my reloads more uniform, thusly consistant in use. Take care and have fun. Swany

I just got my .458 SOCOM brass today myself. Yes, resize them, expand the neck, then check length. Just because they are new cases does not mean they will all the same length. That said, the batch I got did not need trimming. I measured each and every case after sizing and expanding and they all were within .002" of each other, and not anywere near maximum case length. Always check the length, even on new. I have gotten new brass that was at maximum case length, and I have gotten brass that varied as much as .010", which is way too much for working up an accurate load. I prefer it all to be the same, but with this stuff Ed got us measuring so close, it will be close enough for barrel break in and rough load work up. When I fine tune the load they will all be trimmed the same. Don't forget to inside/outside deburr the neck, even if you do not need to trim. And as was mentioned, don't forget to flash hole deburr. There was a lot of flashing in my brass that the deburring got rid of. I got 100 rounds loaded today for breaking in and work up so Monday is going to be a very interesting day. I can't wait!
By the way, I always full length size new brass regardless of straight or bottle neck. Brass can get squished out of round in the body just as it can in the neck. The BBT driver is not always so gentle with the boxes and an egg shaped case can gum up the works pretty quick, especially on the AR-15s that we are using.
One last thing, since we are shooting this stuff in the AR, don't try to do a partial resizing with the FL die like you can on SS and bolt guns. Do the full length resize but adjust the sizer die to just bump the shoulder back a hair. In bolt guns or SS I either neck size only or stop the FL size just a hair before it contacts the shoulder. Do this on the AR and you are going to end up with the rifle not going completely into battery. Do the FL and bump the shoulder back every loading or you'll be cussing yourself pretty shortly.

Some good suggestions here.

I do full-length resize all new brass, although my dies are set up (for bottleneck catridges) to just barely bump the case shoulder back to guarantee easy chambering, yet not overly work the brass.

Then, as Steven listed, some basic case-uniforming operations like trimming, primer pocket and flash hole uniforming, and chamfering.

The primer pocket uniforming and flash hole uniforming really only needs to be done once for the life of the case so it's not really all that big of a chore. Might as well.... every little bit helps and you don't want to get thumped at the range then wonder if your handloads were really as good as they could have been. Trimming and chamfering are not necessarily done every firing, if so, you may have a die problem.

After the inital work and first firing, then I only need to deprime, resize, check for length, clean primer pockets, then clean/expand necks and ready to load again. The actual loading generally takes less time than the brass prep, but brass prep has a big effect on accuracy.

Also, some of the steps you can of course combine if you are using a progressive press.

Mainly it's all about setting up a predictable, repeatable process so you know you'll end up with a quality load.

Sorting brass by weight isn't generally necessary if you keep it separated by lot, but sometimes you get some mixed lots and sorting can prevent some surprises in terms of accuracy and pressure.