Free range brass
(That's like free range chickens, right?
)
Bushmaster has it right. The ranges I frequent have rules abt. not taking any but yr own brass, and yet, I very seldom get hassled about a few selected pick-ups. Something else abt. handloaders is they very seldom discard brass at the range, even if it is no good, because they generally have a scrap brass collection of their own at home, and the no-good brass goes there and is worth so much a pound to them.
There is another good sign of once-fired factory brass: Flattened primers in the absence of die marks or trimming/chamfering. This means the case was SAAMI spec when it went into the gun's chamber, and was stretched on firing. The first thing that happens in that instance is the primer backs out a couple thousandths; the next is that the case stretches to fill the rifle's chamber and therefore flattens the primer. This all happens before the bullet starts to move, I believe. Anyhow, when you find such, Voila! Once-fired case!
I scrounged .30-'06 brass until I had more than I could possibly use. I did the same for friends who shoot .308Win. Next was .357 Magnum. Almost nobody leaves decent .243Win cases on the ground. I recently became the proud owner of a 1911A1, so I grab all the .45ACP I see.
I also grab a few belted magnum cases, with the intent of cleaning and selling them, but have yet to manage a sale as of yet.
Since many people @ my ranges just leave their brass, and since I put the brass I pick up that I DON'T want, in the brass can, mebbe I'm performing a service for the range even if I take some of "their" brass.