What is an AR 15 Dissipator? thumbnail image

What is an AR 15 Dissipator?

Preston Arnet   |   Jan 17th 2020

A Dissipator as it relates to us in the gun community; is an AR15 with a 16” barrel, but with a rifle length front sight. Let’s go over the pros and cons of having one, and finding out if it’s right for you.

The History of the Dissipator (Dissy)

Designed around the Vietnam Era (before reliable and accurate red dot sights) the Dissipator was created by sawing a 20” barrel down to 16”. This made the rifle lighter, shorter, and kept the long sight picture. However, sawing down the barrel messed with the gas timing of the gun, and reliability became a big issue. There is a fair amount of controversy over who actually first created the first commercially available Dissipator, but it is fairly well accepted that Bushmaster released the design first. These days most people build a ‘dummy’ Dissipator, meaning they keep the carbine or midlength gas system to aid in reliability, but stick a front post and gas block at the end of the barrel to imitate a true “Dissy”.

With the longer gas system, a 16" Dissipator will shoot softer than the other gas systems.

Advantages of the Dissipator Barrel

As previously mentioned, the Dissy has a 16” barrel, and a long sight picture, while still maintaining the right timing and reliability. Even past these advantages however, the Dissy also has an incredibly long handrail. This aids in protection from a hot barrel, more space to put lights, grips, bipods, and other accessories, as well as aids in forward hand placement.

A lot of folks build Dissipator builds simply because of how they look. With an old, classic AR15 look, tons of retro and historic Dissy build can be found.

Disadvantages of the Dissipator Barrel

Though reliability has been fixed with carbine or mid-length gas systems, there is added weight from the ‘fake’ gas block at the front of the barrel. Since the weight of the sight/gas block is so far forward on the barrel; it can make the rifle feel a little unbalanced at times, and can be annoying when shooting without a rest. If you intend to make a true Dissy (one gas block at the end of the barrel) you will need to widen the gas port to get more reliable cycling, which will cost you more money and time.

An M16A1 Dissipator with a reflex sight. I'm slightly uncomfortable.

Is the Dissipator Relevant Today?

Honestly, no. The Dissipator was made to fix an issue that holographic sights, red dots, and high quality irons can now fix. While a great solution at the time, technology has advanced and left the Dissipator in the past. That isn’t to say that the Dissy isn’t cool, because it is. It’s historic, and was an important advancement in firearm research and technology. If I was building a rifle with the intent to shoot solely iron sights, then sure I might look at a Dissipator build. But I’m not, and I don’t know many people who would. So I am going to keep my AR15’s in the 21st century with modern furniture, sights, and optics.

Start your Build with 80% Arms today!

Whether you are starting a Dissipator build or not, 80% Arms has the material to get you started! Check out our wide selection of upperslowerssights, and accessories to find the right look and parts for your next AR15!