For years you had to be a member of SAAMI (the Sporting Arms & Ammunition Manufacturing Institute) to get a copy of the data the factories use to manufacture guns and ammunition. The Internet has made is easy for SAAMI to share this data so it is now available for download at their site.
The publications are broken up into books for various types of cartridges i.e. Rifle, shotgun, pistol, and rimfire. So you only download the information you need. This data answers an incredible number of questions for avid shooters. All the tolerance specifications, and pressure data are included. As a bonus the correct methods for testing are described in detail.
In Truth, there is more information provided than most shooters will need. However, if you’re trying to compare cartridges or want to know the standard dimensions for a cartridge, this is must have information.