Dissipator AR-15 w/ M4 barrel profile

[MatthewVanitas]

Greetings. I've read through a few other threads on Dissipators, and am a bit confused as to the weight issue. When using a M4 barrel profile, is the Dissipator notably muzzle-heavier than any other M4gery or Patrolman carbine? A few extra inches of plastic and aluminum handguard and one gasblock can't weigh too much, can it?

On a lot of the Dissipator posts, I'm unsure as to which barrel profile the owner had, so just curious as to the opinions of those who have the M4-profile Dissipator.

I'm shopping around for a short AR-15 variant (trained on M16A2, but I'm only 5' 6", so I have a thing for carbines). I like to be a little different, within reason, but I can't justify owning something novel like a MAS 49/56 or Ljungman as a primary contingency rifle. Now, the Dissipator has the virtues of the shorty AR-15 with a little extra panache, and hopefully a few practical advantages.

I understand that I'd need to buy the barrel and receiver separately, or request BM to assemble them before mailing, as M4 Dissy isn't a catalog item. On the plus side, I'd have the latitude to get a A3 upper and flash-hider of my choice, since it's not stock. I've heard some good things about that new FS with the Slavic name which everyone mis-spells, thus making it hard for me to Google it accurately.

So, then I slap it together with a finished lower of good quality with a good trigger, slap on the stock and grip of my choice (Pachy grip w/ ACE short-stock?), and I'm golden, right?

If anyone has the same rifle I'm describing, I'd love to hear your opinions (and see pics). I've known in my heart-of-hearts that I need a short AR, just waiting for some checks to come in. Thanks much,

-MV

 

[forquidder]

Dissipator

I think you will have to go with a dissipator barrel which is essentially a 16" barrell with a regular A2 forend (long forend designed for a 20" barrel). The dissipator forend would cover the M4 grenade launcher cutout as well as the gas port (the M4 barrel being designed for a carbine length forend), precluding you from being able to mount a gas block.
To gain some weight savings you may be able to get a dissipator barrel with a slimmer profile under the handguard but an M4 barrel will not work.

 

[MatthewVanitas]

I hate to be contrary, but:

Bushy does indeed have a Dissy w/ M4 profile, though not as part of a stock complete upper.

http://www.bushmaster.com/shopping/barrel-assemblies/abbl-16dm4a.asp

The other option being the "Heavy Barrel Assembly".



Some folks have mentioned getting the HB and fluting it, but I'm unsure as to whether that is ultimately lighter than the M4 profile, and probably a bit spendier.

 

[BIGPHIL]

I had an HBAR Dissy barrel. It was basically a 20" HBAR barrel that had been cut down to 16". Mine had the standard length gas tube. The biggest advantage (if there is one) to a Dissy barrel is the standard barrel length sight radius (compared to the shorter length on a carbine barrel).

My barrel was a little front heavy with a collapsible stock. Not so much with a standard A2 stock. If you are wanting to save on the weight, definitely go with the M4 profile bushy barrel in the pic. I dont know how bushmaster works. I have never dealt with them directly. I would think they would assemble it for you.

I have since sold my Dissy barrel. Don't know if I would ever get another. Probably would get just a 16" barrel.

 

[geekWithA.45]

My dissi has an hbar, which does indeed make it balance forward of the magwell, whereas M4geries tend to balance at the magwell.

FWIW, I've found that my rig, which has no muzzle device, has less muzzle rise than an m4gery with a brake.

 

[Bartholomew Roberts]

Another option you might want to consider is a midlength gas-system with a low-profile gas block and a 12" or 13.2" rail system over the barrel. You can mount a front sight to the rail.

This would be a little more expensive; but you would get the same effect with less weight. You could also use any number of custom barrels or barrel-profiles.

 

[forquidder]

Sorry, my bad
Thanks for educating me.
I was thinking that the dissipator model was set up to take advantage of the standard length gas tube and the shorter, lighter weight 16" barrel. Obviously they come in several different barrel configs.
Manufacturers are certainly getting creative these days.

 

[modifiedbrowning]

I've heard some good things about that new FS with the Slavic name which everyone mis-spells, thus making it hard for me to Google it accurately.

http://www.jnrifleworks.com/

 

[Bartholomew Roberts]

I've heard some good things about that new FS with the Slavic name which everyone mis-spells, thus making it hard for me to Google it accurately.

I believe that flash hider weighs in at about 8oz and will contribute to a muzzle heavy feeling on almost any rifle with a barrel over 11".

 

[MatthewVanitas]

I believe that flash hider weighs in at about 8oz and will contribute to a muzzle heavy feeling on almost any rifle with a barrel over 11".

It would appear that you are correct sir; the Noveske FS is optimized for the 10.5" barrel, according to the website. In that case, the A2 will do me fine at a fraction of the price.

Mr Bartholomew: I'm a little unclear as to the model that you're suggesting. Is there a pic available of such a creature? I do like the style of the mid-length 16" (the short-handguard models seem awkard), and there are supposedly some advantages to the mid-length vs. M4 gas system. This might need some more research as I raise funds.

The consensus from folks w/ HBAR Dissys seems consistent: a bit heavy towards the muzzle, but less flippy. Nobody so far with a fluted or M4 profile Dissy?

Thanks, -MV

 

[GoRon]

I have been looking at the 20" they offer and this looks like something BR is talking about.

Link(toward bottom of page)

New MOD4 18" SPR w/Mid-Length Cas System. Barrel is a medium contour and is Chrome Lined 1/7 w/A2 Hider. This upper comes with tapered or oversized handguards and is complete with bolt, carrier and charging handle . CMMG semi auto bolt carriers have the shrouded firing pin and a larger lug on the rear. Upper receivers are "T" marked and include extended feed ramp cuts. 5.56 chamber. New features include, "F" marked FSB and parkerizing under base. When ordering with optional gas block barrels will not be drilled for taper pins.
$549.95

 

[Bartholomew Roberts]

Mr Bartholomew: I'm a little unclear as to the model that you're suggesting. Is there a pic available of such a creature? I do like the style of the mid-length 16" (the short-handguard models seem awkard), and there are supposedly some advantages to the mid-length vs. M4 gas system. This might need some more research as I raise funds.

You would have to go to a custom house like MSTN or ADCO to get the creature I am suggesting (or build it yourself). Basically, it gives you the advantages of the mid-length gas system, with the full sight radius and protection of the longer rail.

You would start with a flattop upper and a 16" midlength barrel. There are a lot of profiles available for these that are more medium-contoured. You would add a rail system. A 12" rail system is the normal rifle-length handguard; but one company (Larue) makes a 13.2" rail system (12" + 1.2" of the front sight base). The low profile gas block will let you put the rail system over the gas block. The downside is you will now have no front sight, so you will have to add one to the rail.

Here is a picture of this concept from glock23carry's post at AR15.com (12" rail with midlength gas system)


Here is another midlength dissipator (feral's from AR15.com) with the same concept:


See this thread for more ideas:
http://www.ar15.com/forums/topic.html?b=3&f=118&t=245191&page=1

The advantage here is you get less weight (lighter 16" barrel profile + only one gas block) but you still get the full 20" rifle sight radius with the 13.2" tube and almost the full radius with a 20" tube. You also get the benefits of the mid-length gas system instead of the shorter carbine gas-system. Downside is we are talking about a $280 rail system, a slightly more expensive barrel and the added cost of a front sight for the rail (both of the pictures show a flip front; but Larue makes a very nice fixed front sight).

The MOD4 pictured above is a more typical midlength. It has both the midlength gas system and the shorter midlength sight radius. The two rifles shown above, have the same gas system but have the longer sight radius associated with Dissipators (as well as protecting you from a hot barrel better).

 

[peabody]

SOOOOO ???


how did your rifle turn out ?


ADCO has the dissy ''cruiser'' barrel's now.. mid-length gas,

lightweight, and so totally awsome


peabody

 

[Tirod]

I've finished assembling my lower for exactly this purpose.

Dissipators are by the classic definition rifle length gas on a 16" barrel. Rifle length handguards are then easily attached, as the FSB is active and retains the front cap for the guards. You get rifle length sights, which for some was an improvement in accuracy.

Lately, some have been using carbine or mid length gas, with a low profile block under handguards, or a free float. The free floats invite the question, is it really a dissapator if there's no FSB out front? There's no consensus yet, and certainly no one in authority to say. Three gun competitor's have gone the long tube route to get their support hand further out for better control.

For a 16" barrel, mid gas is optimum and allows better timing and action cycling. Those barrel profiles come in a lot of variations. Since thicker equals heavier, let that be your guide. Most of the weight seems to be under the handguard, and if a tube is being run, the heavy profile isn't necessary to retain or improve accuracy. The free float does that, and the lighter barrel will be just as accurate as it's not getting moved around by the handguards or sling.

Accuracy improvement is conjectural, there are no real side by side tests to show it.

The next heaviest item after barrel profile is the FSB, in forged steel. Adding another small gas block under the tube/guard is a few ounces out in front of the magwell. A complete FSB, inactive, with handguard cap, will probably weigh more out front that a tube with a BUIS front sight on the rail. Lots of apples and oranges come into it - is it a quad rail with VFG, lights and sling, what type compensator, if any, or even suppressor, would an inactive gas block in aluminum, rail height, with handguards and MBUS in polymer be lighter, etc?

Not to mention, what can be spent? Tubes aren't cheap, they can cost 1/2 the price of a barrel, and you can certainly spent 1/2 more on a barrel and get more accuracy. Decisions, decisions.

Is a HBAR under 20" really necessary? Probably not, although many buy them. All that extra steel is just a heat sink, and we only have semi autos. Most of us don't mag dump, a lot don't shoot a 1000 rounds a year ever. Better accuracy can be had with optics and more practice. Few shoot the limit of their carbine or even see it. If anything, a lighter profile with NO M203 cuts is all we need - and one of the harder to find. It's the nature of the market to sell what we want, not what we should get, since the customer always thinks he's right.

It's a bit more involved than it first seems, and even calling it a dissipator might be a stretch. Nonetheless, for some of us, not having a long piece of barrel hanging out of a short handguard is the end result, and we're happy with it.

 

[Al LaVodka]

Assorted

)

Al

 

[Jguy101]

Necrothread...

 

[Tirod]

Not if your building one. Frankly, that's the whole point of the internet - to share lessons learned and information gathered by others to the questions at hand now.

Case in point, the one DISADVANTAGE of the dissipator may be the Vltor Volks suppressor needs a few spare inches behind the muzzle because of it's mount. No sense eliminating an option that delivers more than most of the tacticool bling on the market. Being able to hear and communicate over the sound of firing is more important than spending the same money for a few % more reliability or accuracy in some other component.

Instead of $1200 for a Trijicon, how about a suppressor and Aimpoint for the money?

From a builders' perspective, the challenge of a suppressor and intermediate handguards, or the justification to put a tube on it, no intermediate handguards being on the market?

Who wants to build the same old thing? "Oh gee another black M4gery. Ho hum." Seems like the most popular threads on the net are someone seriously modding a 80% lower in their basement machine shop, or having a piece of real use gear most won't ever get.

 

[peabody]

i used a trimmed down cmmg barrel, 16'' with the gas port moved to mid-length, a low pro gas block, under the guards. and a A.R.M.S model 41-B for a front sight. using a cutt off gas tube to index the triangle cap.
flattop with a cnc A1 carry handle, and SX same plane rear sight.
its turning out to be, a little bit of everything, best of both worlds.
just ordered a david tubbs recoil spring.oh, and a three prong weed snagger for a flash hider.
M4 stock .
yes. its a mutt. but its turning out very well.
thinking of grinding off the case deflector, [its fugly] ...
and putt on a tear drop FA. [gotta always have some ''retro'']
peabody