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Americans have guns at home, therefore the reserve forces are much greater in number than the armed forces.

42% of 327mn is equal to 137mn people with mostly semi automatic firearms.

https://www.washingtonpost.com/news/wonk/wp/2018/06/19/there-are-more-guns-than-people-in-the-united-states-according-to-a-new-study-of-global-firearm-ownership/

Good luck!!