Adams Arms Dissipator Rifles and Uppers

Adams Arms recently debuted their new line of Dissipator rifles and uppers. What’s a Dissipator you ask? It’s essentially an AR-15 with a 16″ barrel and a rifle-length gas system. Why would you do that? Mostly for the benefits of the longer rifle-length sight radius and shorter and more maneuverable 16″ carbine barrel. And because it looks pretty cool. Here is a pretty good read on Dissipator AR-15s.


Adams Arms new Dissipators use their lightweight Ultra Lite VooDoo 16.5″ barrel coupled with their AR-15 short stroke piston system and Magpul MOE furniture. They also come with a low mass Adams Arms bolt carrier group that’s 21% lighter than their other carriers, weighting in at just 7.5 ounces. According to Adams Arms their Dissipator uppers and rifles run cleaner and cooler all the while maintaining a very low felt recoil pulse. Their Dissipator upper retails for $815.38 while their Dissipator Rifle retails for $1326.32, both come with a lifetime warranty from Adams Arms.

Adams Arms Dissipator Rifle Specs

– Mil-Spec Forged 7075-T6 Lower Receiver, Type III Class II Hard-coat anodized finish, beveled magwell, machined chevrons in front strap
– Mil-Spec Forged7075-T6 M-4 Upper Receiver, Type III Class II Hard-coat anodized finish, M4 feed ramps, 1913 Picatinny rail flat top with dry lube internal finish and laser engraved T-markings
– 16.5″ Ultra Lite Contour 4150 CM Melonited Barrel 1:7 twist
– Chambered .223/5.56 x 45 mm NATO
– Magpul MOE® Rifle Stock
– Low Mass Bolt Carrier
– Magpul MOE® Grip
– Magpul MOE® Hand Guard and Trigger Guard
– 30 round Magpul PMAG
– Diamondhead D45 Swing Sites (optional)

Adams Arms Dissipator Upper Specs

– Low Mass One Piece Bolt Carrier 7.5 Oz (21% Lighter)
– VDI LifeCoat 16.5” Ultra Lite Rifle Length Match Grade Barrel (.750 Gas Seat)
– This Match-Grade barrel is precision honed, creating a smooth round and straight hole
– Chambered 5.56x45mm NATO 4150CMV 1:7 Twist
– DiamondHead D45 Swing Sites (optional)
– Magpul MOE Hand Guard
– Weight: 4.6 lbs
– Made in the USA
– Life-Time Warranty

Ray I.

Long time gun enthusiast, archery noob, Mazda fan, Sci-Fi nerd, Whiskey drinker, online marketer and blogger. My daily firearms musings can be found over at my gun blog and Instagram.

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  • G2022

    Wow,. Adams arms gets more coverage here than Hillary Clinton gets on CNN. New sponsor?

    • Geez again. Ok for the 1137th time we don’t know who’s advertising. They seem to be doing a lot lately so they get the coverage.

    • Secundius

      @ G2022.

      Adams Arms, is no longer paying their advertiser, and may be going out of business.

  • dp

    I spotted some vagueness in attached article.
    First: perception of pressure building up along the barrel length is not correct. With expansion, the pressure drops, it does nor increase. Pressure peaks while bullets is just about released from crimp and enters rifling throat (forcing come. This takes some 0.2-0.3 m/s since firing pin strike. After that it progressively drops (gas passes heat into barrel in addition to expanding) You cannot ‘chase-up’ pressure magnitude by length of barrel.
    Second: its is not just gas port location on barrel what counts, although it determines initial entry pressure. It is also the leftover length from port to the muzzle. This represents duration for which the pressure acts to drive (presumably reliably) recoiling mass. Conversely, if you want to obtain same amount of work required for this function on short barrel, you have to appropriately enlarge the gas passage. However, this promotes quicker venting of gas pressure and is rather counterproductive. It is like vacuuming your room with open windows.
    Overall, problematic involved points to inherent shortcoming of DG system; it does not provide lots of flexibility for reliable function under variety of conditions. For that reason alone the piston driven system is and will remain vastly superior. The only historical reference is Swedish Ljungman (and its Egyptian derivative) rifle which was in service just couple of years and was rather quickly replaced by rifle of conventional (piston) system. Finally, it ought to be stated that there is a difference between one ‘home-built pimped-up’ system and repeatable industrial production and this should be taken to consideration.

    • dp

      Little typo intruded, please correct:
      In fourth sentence “forcing come” should read: “forcing cone”.

  • dp

    This note is little bit away from subject, but it is still relating to it.
    It is due mention of rifle and MG systems from 20’s – 40’s of last century. Those early auto and semi-auto systems had typically their gas tap close or even very close to the muzzle and yet, they worked just fine and many were considered utterly reliable. One benefit for sure was long delay between cartridge priming and pressure input into return mechanism which in turn gave very manageable rate of fire. True “dissipators” you might say.
    That was enabled by fairly massive return system and resulting favorable ratio between primary (operating rod) and secondary mass (bolt). Operating rod is a convenient energy storage and this is ‘secret’ behind the AK weapon system. But, for time being this will not add anything to favored and prevalent AR system and I realize it.

    • iksnilol

      Reason those old designs worked well is because they had a long gas piston/op rod.

      An AK works just fine if you cut the barrel down to the gas port. Because when the piston is long then the gas starts pushing it immediately instead of building up before pushing (dwell time).

  • DoubleMonocle

    I have always been under the impression that a dissy is a carbine length gas system with a low profile gas block to fit under the hand guards and a FSB mounted at rifle length position on the barrel. Isn’t this just a rifle length piston system on a 16 inch barrel?

    • DoubleMonocle

      Read the provided link, what I described just serves to increase sight radius, so I guess that kind of misses the point of the dissy…

    • Cornelius Carroll

      Originally dissys were 20″ barrels with rifle gas cut down to 16″. Later they enlarged the gas port to improve reliability (this is how DelTon currently manufactures their dissys). Later, manufacturers started using a mid-length gas system with an A2 fsb pinned to extend the sight radius. IMO, this is the most reliable configuration. I’m sure some manufacturers have also done the carbine length gas thing but, IMO, on a 16″ barrel carbine length is over-gassed.

      • Andy

        Agreed. It’s a shame the mid-length setup doesn’t get more love, especially with a 16″ barrel.

        • M

          Mid-lengths are growing in popularity because it simply makes sense performance-wise.

          Part of the reason it didn’t was due to cost reasons for companies with defense contracts: why spend the time to do something different when you can just turn down a 16″ barrel the same way as a 14.5″? This is the same reason we had two flavors of barrel profiles for so long…

          Also, there will always be those people who want to buy “the gun the military has” so M4geries are here to stay

    • Could I ask what a Dissy (abbreviation/nickname) stands for? I’m a newb, and am trying to learn.

      • Cymond

        Dissy is short slang for Dissipator, the style of upper discussed here.

        • I sir, let that totally fly over my head.

          Feel embarrassed for asking…

          Thanks though!

  • Dracon1201

    Well, I ordered one 2 days ago. We’look see how this goes!

  • dan citizen

    I like the looks of this one, kind of FAL-ish (though I don’t really like FALs)

  • thedonn007

    So, the barrel is not chrome lined?

    • mig1nc

      Melonite is superior to chrome lining in pretty much every way. As long as it is done right.

      • thedonn007

        Ah, yes I missed that. I prefer Melonite to Chrome lining anyway. I thought that it was not coated at all. Thanks for correcting me.

  • Mystick

    Looks better than the “unlimited rails” that everybody is putting out today. Probably feels better to handle, too.

    • JusticeM4

      The ‘unlimited rails’ is used so you can easily mount accesories e.g. bipod, laser, flashlight (all at once or one at a time). It’s not a look, but a functional configuration for some. If you don’t have a need for them, then don’t buy one with the rails.
      Keymod rails are the new thing now…

      • Mystick

        I’m just saying they are uncomfortable to handle and fire without bulky rail covers. I’ll put a rail where I need a rail. Everything else is added weight.

  • USMC03Vet

    Not even going to lie, that is one hideous looking AR15.

    • Cymond

      I love the Dissipator look, and it made a lot of sense before the rise in optics, low-profile gas blocks, and free-float handguards. Today it’s a little bit more of a retro concept, but it’s still a very durable option for those who like a fixed front sight base.
      I have a “Kino” pistol upper that’s a very similar concept, except it’s a 12.5″ barrel with midlength handguards and a low-profile gas system under the handguards (pics not mine).
      But I do think Dissipators look weird without a fixed front sight.
      Edit: That image was NOT supposed to post twice.

      • BattleshipGrey

        I really like the mismatched furniture. Very cool!

        • mig1nc

          Me too, man you made a downright work of art there.

          • Cymond

            Well as said, the pics aren’t mine. I saw this a few years ago and liked it enough to save it, to remind me to try it myself eventually.

      • mig1nc

        To be fair, you can put a fixed front sight on the Adams gas block. If you want. I think they were smart to do it that way, so you can put flip ups or fixed, depending on your preference.

        • Cymond

          Yeah, I know it’s more practical this way, it just looks a little odd on an already odd design (Dissipators are odd). At some point, it becomes more practical to use a free-float handguard. Personally, I think Magpul MOE handguards are not very light.

  • wicked_bear

    I think these are cool, toss on some flip-up sights, and your GTG

  • Secundius

    I don’t know? I looks to much like FN-FAL too me.

    • BattleshipGrey

      I consider that a good thing.

  • Cymond

    I stated thinking, and this might make a LOT of sense with the AA piston. Dissipators have a very short “dwell time” when the bullet is in front of the gas port. Most builders compensate by using a larger gas port. The result (I suspect) is a rifle that gets a lot of gas for a very short duration. It seems like that would work really well with a short-stroke gas piston.

  • iksnilol

    Late to the party but:

    Wouldn’t a rifle length gas system cause problems if you used it with a carbine barrel? In regard sto dwell time. I thought they just added another gas block to mount a front sight on.