308/7.62 Varies
308/7.62 Varies considerably between brands, and military is thicker and heavier, reducing case volume, but it still varies quite a bit in certain other parameters.
In a nutshell, I recommend you buy one brand of commercial brass. Starline would be good. I have used Rem, too.
But unless you have a lot of experience in brass prep, you should steer clear of military for these reason:
1. All available military 7.62 brass was fired in machine guns. These tend to have sloppy and generously sized chambers, and the brass will come to you "puffed", crimped, and with huge variations in case length. There are exceptions and long Range or match brass can be found, but cost more.
2. They take a special materials, techniques, and skill set to size: very strong O type press, excellent lube (Lucas White Lithium grease is all I will use), crimp needs to be removed (I use a countersink drill bit).
3. They must be trimmed to a useable length.
4. You will want/need to anneal them very soon, because of the hard use (machine gunning puffing and then re-sizing).
3. You WILL want small base dies if feeding an auto-loader. I remove the neck expander from one of my FL sizing dies. Some folks use a 30-06 sizing die as a half step (working the base) die.
4. Breaking the work into steps helps me isolate where something is an issue, then I deal with that issue.
5. Then you should sort them by weight and measure the capacity of each case. The goal is to get a set of very similar brass for consistent results.
Or just buy a batch of quality commercial brass.
Military 7.62 has its uses. I prefer using military 7.62, for auto loading rifles like an FN-FAL, or other gas gun. These guns are a lot harder on brass than bolt guns, and consistency is less critical.