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Choosing the Right Ammunition: Data Stamps

In order to select the right caliber or gauge of ammunition for your firearm, you must locate the data stamp. The data stamp will tell you the correct ammunition to use—for example, .300 Win Mag ("Win" is short for Winchester. "Mag" is short for magnum). You must also decide on the bullet size, expressed in grains (for example, 150 grain or shot size), that you will need to use for the game you are hunting. If you do not match the ammunition to the firearm, the cartridge could become lodged, explode and cause serious injury to firearm user or bystanders.

Data stamps can generally be found on the barrel of the firearm.


Some firearms made before 1964 or ex-military firearms may not have a data stamp. In this case, a gunsmith can help you determine the correct ammunition for your firearm.

Sometimes the data stamp on a firearm may be given in European terms such as 7.62 x 51mm (bullet diameter x case length).

Be very careful to make sure the ammunition matches the data stamp. .300 Savage, .300 Win Magnum and 300 Weatherby Magnum have different cases and are not interchangeable.

Remember the basic rule: If the data stamp on the firearm does not match the data stamp on the ammunition, do not use that ammunition.

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