Here's an interesting article on the subject: http://kitup.military.com/2014/07/sof-prefers-9mm-45-caliber.html

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The Army�s Delta Force adopted .40 caliber, but the elite unit is having the same problems as the FBI � the heavier caliber is causing excessive wear problems in guns that were originally designed to be 9mm. Delta is now using 9mm Glock 17s, 19s and 34s.


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The 75th Ranger Regiment and Special Forces units use M9A1s and Glock 19s.

SEAL Teams mostly use the Sig Sauer 226.

DEVGRU, or SEAL Team 6, does use Heckler & Koch .45 for special occasions when they need a suppressed capability.


Marines seem happy with their 1911's in .45 ACP but they're having logistical issues getting .45 ACP ammunition. If you ask me, that's completely intolerable.