AR-15 = Semi-Auto civilian rifle
M4 = Select Fire Military rifle
The M4 is capable of automatic fire, the AR 15 is not
No.
The US Army presently uses the M4 carbine, a shorter and much modified version of the Armalite AR15.
AR15, M16, M4, Ruger Mini 14
Law Enforcement
Both are assembly line weapons. Stag in my opinion also has a better reputation. Unless you decide to go tactical, they are all pretty much the same. Bushmaster, dpms, stag ext..
AR 15 - semi-automatic only M16 - depending on variant capable of full auto or burst fire. Will also fire semi-auto.
M4 is the carbine- shorter barrel
Their is no NATO M4. NATO countries that use the M4 either contract the purchase or license the production.
100 miles taking A483 NEWTON from Welshpool to M4, and then the M4 MOTORWAY to Swansea.
There are a large number of differences based on the models of both guns, however the most notable is that the AR15 is a semi-automatic and the M16 is capable of semi-automatic or full automatic.
The basis of the M4 is the M16 rifle, for which Eugene Stoner is commonly credited. Development of the M4 was a cooperative effort between the Special Operations Community of the United States Armed Forces and Colt's Firearms.