# What does firearm caliber measure?

**URL:** <https://boards.straightdope.com/t/what-does-firearm-caliber-measure/261827>\
**Category:** Factual Questions\
**Created:** [August 27, 2004, 7:09pm UTC](https://boards.straightdope.com/t/what-does-firearm-caliber-measure/261827 "2004-08-27T19:09:37Z")\
**Posts on this page:** 1\
**Page:** 2

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**Author:** ![David\_Simmons](https://avatars.discourse-cdn.com/v4/letter/d/9de053/32.png) [@David\_Simmons](https://boards.straightdope.com/u/David_Simmons)\
**Post date:** [August 28, 2004, 8:53pm UTC](https://boards.straightdope.com/t/what-does-firearm-caliber-measure/261827/21 "2004-08-28T20:53:24Z")

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> [@JRDelirious](#):
>
> Very few weapons will fire properly, or even function at all, if loaded with different-from-spec ammo, and the few that do accept only a minor variation – the most notable being a .357 Magnum revolver, which will easily fire .38 Special rounds because they are just shorter and with a lighter load than the .357 Mag, but otherwise fit the chamber exactly. With almost any other weapon, wrong ammo will either not work or damage the weapon, perhaps catastrophically.

[anectode] In the movie _Sergeant York_, Gary Cooper as York uses a Luger. York used a Colt .45 which was standard Army issue for non-coms. A Luger had to be used because the blanks that were used didn’t have enough kick to operate the slide on the Colt.[/anectote]

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