Most everyone who received a free airplane ride to Southeast Asia courtesy of President Lyndon Baines Johnson in the late 1960s soon figured out that there was a need for a shorter weapon in the dense jungles of Vietnam. Colt, the original manufacturer and supplier of M16 rifles to the U.S. Military, lopped off 5 inches from the M16’s 20-inch barrel and called the resulting 15-incher the 605, making it the first AR carbine. What was unique about the 605 was it used a carbine-length barrel with a rifle-length gas system. These abbreviated M16’s have become known as Dissipators. Kentucky’s Anderson Manufacturing calls its interpretation the AM-15 Dissipator.
Chopping down the barrel lightened the M16 rifle, as well as made it shorter and more maneuverable in heavy vegetation. The idea seemed good on paper, but in practice the 605 rifle was unreliable. The 15-inch barrel reduced dwell time drastically. Dwell time is the amount of time the bullet stays in the barrel past the gas port. Reduced dwell time drastically affected reliability, and a “fix” in some cases was adding a suppressor to increase back pressure. Colt continued to experiment with short-barrel M16s and eventually developed the 609/610 or the CAR-15. Colt never called the 605 the Dissipator, nor was it ever put into production, but a cult-like following emerged around the first M16 carbine. Bushmaster commercially produced a 605 clone and called it a Dissipator due to the rifle-length hand guards with metal inserts that dissipated the heat from the barrel. The name stuck for any AR-15 with a carbine-length barrel and rifle-length handguard. Bushmaster also used a carbine-length gas system for enhanced reliability. Other commercial AR-15 manufacturers built their versions of a Dissipator and, like Bushmaster, used a carbine- or mid-length gas system. Anderson Manufacturing, however, opted to keep the rifle-length gas system like the original 605. To increase reliability, the folks at Anderson enlarged the gas port to allow more gas to flow and I found no issues with reliability. In fact, the rifle-length gas system has advantages over a carbine-length gas system. It offers less felt recoil because it has a smoother recoil im- pulse. Two-hundred rounds proved this is a nice-shooting carbine.
While the AM-15 Dissipator has its DNA in the original Colt 605—think triangular handguard and duck-bill flasher hider, Anderson’s variant features some updates using both M16A2- and M16A4-style components, so while it has a retro look, it also has contemporary features.
The 16-inch barrel has a government profile and a 1:8-inch twist rate with an A2-style front sight with integral gas port. An A2-style bird- cage muzzle device is screwed onto the muzzle. The front sight is adjustable for windage and includes a bayonet lug and sling swivel. The sight will be very familiar to those who cut their teeth on the M16A2 through the M4. It’s a rugged, reliable front sight.
Furniture includes a fixed, A2-style buttstock with the fixed sling loop, and the old-school, A2-style pistol grip. The round, two-piece clamshell handguard is also A2-style and held in place with a delta ring. Each half of the handguard has a sheet metal shield inside it to—you guessed it—dissipate the heat from the barrel and gas tube. The A2 handguard was designed well before the aluminum quad, KeyMod and M-Lok rails we use today. Don’t expect to hang any accessories from the AM-15’s handguard. The Dissipator was designed in an era before tactical lights, vertical grips and lasers became standard equipment. Sure, it’s old school and that is the intended vibe with the Anderson AM-15.
The upper receiver is an A4-style flattop. Original uppers on the 605’s and Dissipator clones had a built-in or removable carry handle that also housed the rear sight. The AM-15 is set up with a Magpul MBUS folding rear sight. The flattop upper gives the AM-15 Dissipator a modern look and offers plenty of rail to mount an LPVO scope or red-dot optic—a red dot would be near perfect for the AM-15. I opted to run the AM-15 Dissipator as is with the iron sights to get that true retro experience. Besides, I like the fast acquisition peep sights offer. Of course, you could also add a removable carry handle to go all in on the retro look. The lower receiver is also a mil-spec style M4 without the M16 trigger pocket.
Anderson ships the rifle with an aluminum 30-round magazine manufactured by ASC. The metal mag supports the retro aesthetics, especially with the preponderance of polymer magazines in modern AR-15-style rifles. Personally, I prefer the metal variety of magazines. I like the slickness of metal against metal when performing a reload, but I also used polymer Magpul Gen3 magazines and metal variants from SureFeed (made by Okay Industries) and DuraMag during testing.
The AM-15 was a smooth operator and I found accuracy quite pleasing considering I was shooting inexpensive ammunition. Accuracy across all ammo brands was solid.
The AM-15 Dissipator ran exceptionally. It spat out empties where they should go, so there was clearly no over-gassing the system. The trigger pull measured 7 pounds and while that is too heavy for precision work, it is quite serviceable for defense.
For me and others, the AM-15 Dissipator has that old-school coolness about it. It is both nostalgic and eclectic, and yet it is also practical. I would not think twice about using it for home defense.
After all, just because it’s retro- looking doesn’t mean it won’t perform well.
