The Model 609 has a forward assist while the Model 610 does not have one. The Model 607A was made with XM16E1 receiver with forward assist and a standard pistol grip. The Model 607 CAR-15 Submachine Gun was a compact weapon with the first models made with M16 receivers without the forward assists and a shortened pistol grips from the CAR-15 Survival Rifles. The burst cam on the Model 605B could be modified to two-round or six-round burst. The Model 605B had no forward assist, but had a four-position selector switch which has a 360 degrees motion that could move clockwise or counterclockwise. The Model 605A CAR-15 Carbine was a shortened version that can be brought aboard in vehicles or helicopters. The CAR-15 Heavy Assault Rifle M2 is similar to the M1 but instead of a 30-round magazine, the M2 is a belt-fed. The CAR-15 M1 was designed to feed from a 30-round box magazines. The CAR-15 Heavy Assault Rifle M1 was a heavy-barreled version of the standard CAR-15 with a bipod attachment which is intended to be use as a Squad Automatic Weapon (SAW). The Model 603 CAR-15 Rifle was adopted by the United States Army as the XM16E1 and then later as M16A1, and the Model 604 CAR-15 Rifle was adopted by the United States Air Force as M16. The CAR-15 was a family of M16 rifle based firearms. For example, the 9×19mm is pronounce as 9 by 19 millimeter.ġ973 Colt AR-15 SP1 with slab side lower receiver The “×” in cartridge names are pronounce as by. For example, 9×19mm refers to a bore diameter being 9mm and has an overall case length of 19mm. The second number reflects the case length in inches or millimeters but again, usually measured in millimeters. The first number reflects the bore diameter in inches or millimeters but usually measured in millimeters. The two numbers used in cartridge names are the length for modern cartridges. This list can also be use to find firearms base on the AR platform for your OC to use (though most of them are not that unique by external design but most are unique in mechanical design and/or cartridges use). This is here for assisting with distinguishing AR-15/M16 platform from very known based firearms such as the M4, M16, and the HK416 along with additional information (I will improve this list over time).