The AR15 can be considered a somewhat legendary assault rifle. The original AR15 was a battle rifle designed and manufactured by ArmaLite. The design was eventually transferred to Cold and evolved into the Colt M16 battle rifle which was officially adopted as one of the battle rifles of the United States armed forces in 1963. The civilian variation of the M16 rifle still carries its original AR15 designation. The AR15 and M16 continually evolved into rifles with an extremely high degree of customization. Modern AR15 civilian rifles have a plethora of parts and accessories available. The civilian AR15 differs from the military M16 only by not having selectable fire modes. The AR15 is exclusively a semiautomatic rifle. It is essentially illegal to own an automatic rifle, so the AR15 should not be modified for fully automatic fire. However, with the exception of a semi-automatic fire mechanism, the AR15 has nearly identical specs and customization options to the M16. Most AR15 parts and accessories can be used on the M16 and vice versa. Parts and accessories that affect ease of use, accuracy and weight are available for purchase. Basic replacement parts made from lighter materials are also available and you can basically remake your rifle from scratch if you want to, with the exception of some basic parts. The basic AR15 parts make it a highly impressive rifle, but its customization options is what makes it truly shine as a weapon, despite the design being over 50 years old.