“Before addressing the verbs “keep” and “bear,” we interpret their object: “Arms.” The 18th-century meaning is no different from the meaning today. The 1773 edition of Samuel Johnson’s dictionary defined “arms” as “weapons of offence, or armour of defence.”
“Although one founding-era thesaurus limited “arms” (as opposed to “weapons”) to “instruments of offence generally made use of in war,” even that source stated that all firearms constituted “arms.”
“Some have made the argument, bordering on the frivolous, that only those arms in existence in the 18th century are protected by the Second Amendment. We do not interpret constitutional rights that way. Just as the First Amendment protects modern forms of communications,…and the Fourth Amendment applies to modern forms of search, …the Second Amendment extends, prima facie, to all instruments that constitute bearable arms, even those that were not in existence at the time of the founding. DC v Heller, pages 7-8