Long Action vs Short Action - What length do you need?

When ordering a chassis or stock, you'll be asked if you have a long-action or a short-action cartridge. This refers to the size of the opening on the bottom of your action to accept varying lengths of cartridges.

Common Short-Action Cartridges: .243 Win, the Creedmoor family (6.5 Creed, 22 Creed, 25 Creed, 6 Creed), 6.5 PRC, 7mm-08, 308 Winchester.

Common Long-Action Cartridges: .270 Win, .30-06, .300 Win Mag, 7 PRC, 7 Backcountry, 7mm Rem Mag, .300 PRC.

The photo below illustrates the difference between long and short action.