What the heck is an AR-15 dissipator?
To be honest, it sounds like something out of a sci-fi flick. But it’s not. It’s a real term within the gun world.
By this point, you’re likely scratching your head wondering what it means.
So, fear not…
Today, we’re tackling AR-15 dissipators to help you get spun up. We’ll go over the definition, pros/cons, and whether the design is still useful in this day and age.
Table of Contents
AR Dissipator Defined
A “dissipator” or “dissy” is an AR-15 with a 16-inch barrel but with a rifle-length front sight post.
There’s some controversy about who invented what, but they can first be seen in Vietnam era photos.
Why were they used, you ask?
The concept of the dissipator hinged on two positives:
- A shorter barrel allows better maneuverability and weight savings
- A longer sight radius allows for better accuracy
How Were They Created?
Original designs were created simply by cutting down existing 20-inch rifles down to 16-inch. However, this led to reliability issues due to changes in the overall timing of the rifle.
Cutting down the extra 4-inches reduced the “dwell time” which is the amount of time the weapon maintains pressure so it can cycle.
You can think of it as the amount of time the bullet stays in the barrel after it passes the gas port. In the dissipator barrel below, there’s almost no length left for the bullet after it passes the gas port which made the weapon unreliable.
Bushmaster came out with the first civilian AR-15 actually called the Dissipator which had shaved-down gas blocks at the normal carbine length and then a “dummy” A2 sight block up in front at the rifle position.
While no longer made new, they can be found on places like Gunbroker.
PSA also offers their mock version of the dissipator with a mid-length gas system.
However, there are still some “real” dissipators out there with enlarged gas ports and just one real front sight/gas block at the rifle position that have since solved the reliability issues. Del-Ton is the one that stands out.
Pros & Cons
We’ve already gone through the major pros with shorter barrels and a longer sight radius.
Some other advantages include a longer handguard which allows a more forward hand placement, protection from a hot barrel, and more space to accessorize.
And lastly, they bring an old-school kind of cool that resembles a short-barreled rifle (SBR) from far away.
Some of the cons include reliability and weight.
While reliability has mostly been fixed with gas blocks at carbine or mid-length positions, this adds additional weight from “dummy” gas blocks/sights at the front and longer handguards.
But, “real” dissipators with just one gas block at the rifle position also have fixed the weight issue with enlarged gas ports.
Is the Dissipator Still Useful?
With today’s free floating gas tubes and shift toward optics, does the dissipator still have a place?
Our answer is yes, if you are ONLY going with iron sights.
Otherwise, there are too many other options to get the same advantages of a shorter barrel and more accurate sights with a reliable red dot and holographic sights.
Now if you’re making a cool clone rifle, then there is always a place for the Dissy. But you should go with one that is properly made so it can be reliable.
While AR-15 dissipators aren’t as popular these days as they were during the Vietnam era, they still are a cool feature — especially when viewed through the lens of history.
Did you know what a dissipator was? Let us know in the comments below. Also, be sure to check out our definitive resource for all things AR-15 Rifles.