No really easy or 'Simple' answer to this one without more info...
Depends on auto loader or bolt rifle, speed gun or hyper accuracy rifle, ammo blaster or something that will put meat on the table or punch one ragged hole at range...
Since I don't shoot factory new brass very often, I don't test with factory new brass.
Despite the propaganda from the brass companies, it's still JUST a hunk of brass, no more, no less...
Even if you pay $5 or more each new, you SILL have to prepare it for YOUR rifle.
Other than hardening, it's STILL just a hunk of brass, and you CAN anneal it & prepare it again... and again... and again...
Ask ANY bench rifle shooter.
This is a point I got into an argument about (on line) about,
*IF* you are a 'Reloader' (not 1 time loader) the entire point is to reload, that by definition makes most of what you shoot fired more than once.
Going back in the same rifle (auto loading excluded in a lot of cases),
You only take enough out of the case to get it back into the chamber,
And there isn't ANY factory brass going to make brass that 'Specifically' fits YOUR particular chamber, you have to fire form to get that...
With auto-loaders, or with building ammo for MULTIPLE rifles,
You often have to beat the brass back very close to SAAMI specification so it chambers/functions in all firearms.
Just ONE tight chamber in the bunch, or a semi-auto that won't load a bloated case, and you are back to pretty much SAAMI to get them cycling.
For semi auto calibers, I've gone to case rolling, then annealing, then full length sizing & trimming so the brass is as close to factory/SAAMI as I can make it.
I have ZERO idea what my bulk brass customers are doing with it, so SAAMI is 'Safe' for everyone, from the guy with the ultra tight chamber in his 'Varmint' rifle to the guy with the 'China' barrel AR that would load about anything this side of a .308 case...
I learned from speed gun matches that rolling pistol & semi-auto rifle cases to SAAMI specs reduced failure to feed to about ZERO.
Speed gun matches you aren't shooting with hyper accuracy, so the case fitting the chamber to the Nth degree isn't an issue, while feeding & reliability is everything.
When I'm knocking out longer range rounds, I have specific die sets for those rifles to beat the brass back just enough to chamber correctly.
One thing I can tell you from personal experience,
That ultra tight chamber, ultra tight neck in the chamber *Sounds* real good!
Wait until you are in the middle of a match and suddenly find one of your rounds WON'T CHAMBER!!!
That super tight neck sized to the Nth degree jams up a round where you can neither get the bolt open or closed, and you WILL rethink your approach!
If you own more than one rifle in a specific caliber, sooner or later that precisely neck turned ammo WILL find its way into the 'Wrong' rifle, just a fact of life...
After years of bench rifles, and years of 'Custom' rifles, I've come back around to making the brass mostly SAAMI, and keeping the chamber close to SAAMI so anything close fits reliably.
I still cut chambers in a 3 cut process most times, but auto-loaders & bolt rifles get 'Different' chambers.
(The same way machine guns get different chamber profiles than accuracy rifles)
