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9/22/2017 12:11:25 AM
Posted: 8/8/2005 4:43:13 PM EDT
I thought the whole idea of a dissipator was to have a 16'' barrel with a rifle length gas system resulting in a smoother action. However, as I just flipped through my bushmaster mag, it says the gas block is located under the handguards at more of a carbine length, which dissipates heat better, hence the name.

How does this placement help with heat? This makes no sense to me.
Link Posted: 8/8/2005 4:51:52 PM EDT
[Last Edit: 8/8/2005 4:53:51 PM EDT by Lancelot]
It doesn't make the heat less. It keeps the hotest part of the barrel, the gas block, under the handguards where it wont' burn you. It is a carbine length gas system.

And the idea was to give you a carbine length barrel with the longer sight radius found on a rifle.

You can cut down a 20 incher / rifle length gas system and make it a dissy-clone. But that would require opening up the gas port.
Link Posted: 8/8/2005 4:53:36 PM EDT
The only thing that it looked like it might improve is accuracy, with the front sight much further out you would have a better sight radius. I would think that the handguards being longer would hold in more heat
Link Posted: 8/8/2005 4:55:54 PM EDT
The longer sight radius makes sense, and the bushmaster mag states that as well. But is also says this setup dissipates the heat better. Page 11 if you have a copy.
Link Posted: 8/8/2005 4:57:35 PM EDT

Originally Posted By Reload_em:
The only thing that it looked like it might improve is accuracy, with the front sight much further out you would have a better sight radius. I would think that the handguards being longer would hold in more heat



Indeed the longer handguards on the carbine barrel help dissipate the heat from the barrel. Oh hey look at that! It's a Dissipator...........
Link Posted: 8/8/2005 5:03:49 PM EDT
Why the effort to move the gas block back, why not just use the rifle handguards and gas length with a 16 inch barrel?
Link Posted: 8/8/2005 5:10:14 PM EDT

Originally Posted By Szurgot:
Why the effort to move the gas block back, why not just use the rifle handguards and gas length with a 16 inch barrel?



Because it is a 16" barrel. They didn't have to move the gas block they had to move the front site.
Link Posted: 8/8/2005 5:15:48 PM EDT

Originally Posted By sysop:

Originally Posted By Szurgot:
Why the effort to move the gas block back, why not just use the rifle handguards and gas length with a 16 inch barrel?



Because it is a 16" barrel. They didn't have to move the gas block they had to move the front site.




Yes, but on a normal system the front sight is the gas block. Why use a separate gas block and front sight when you can use a combo one at rifle length with a 16 inch barrel.
I am not arguing, I just dont see the point of a shorter gas system when you dont have to.
Link Posted: 8/8/2005 5:21:05 PM EDT
Link Posted: 8/8/2005 5:23:10 PM EDT

Originally Posted By sysop:

Originally Posted By Reload_em:
The only thing that it looked like it might improve is accuracy, with the front sight much further out you would have a better sight radius. I would think that the handguards being longer would hold in more heat



Indeed the longer handguards on the carbine barrel help dissipate the heat from the barrel. Oh hey look at that! It's a Dissipator...........



Since we all know that heat rises, the only way that the so called "dissipater" can get rid of heat, is to only shoot into the air. It is about the hottest overheating gun out there.
Jack
Link Posted: 8/8/2005 5:27:28 PM EDT
Answer me one more question, and then we can let this topic die. With different length gas systems there would be different pressures and therefore a different "feel" when shooting
correct???
Link Posted: 8/8/2005 5:34:40 PM EDT

Originally Posted By Szurgot:

Originally Posted By sysop:

Originally Posted By Szurgot:
Why the effort to move the gas block back, why not just use the rifle handguards and gas length with a 16 inch barrel?



Because it is a 16" barrel. They didn't have to move the gas block they had to move the front site.




Yes, but on a normal system the front sight is the gas block. Why use a separate gas block and front sight when you can use a combo one at rifle length with a 16 inch barrel.
I am not arguing, I just dont see the point of a shorter gas system when you dont have to.



They are supposedly more reliable with the shorter gas system. The first dissy I got was a KurtGeweher made by Kurts Kustom Firearms who is an industry partner here. Even with a full length system, it runs like a scalded dog even when fed Wolf ammo but it has had Kurt's majick touch. I just got my second dissy upper and it has the shorter gas system; so I cannot compare them at this time.

wganz

Link Posted: 8/8/2005 5:36:07 PM EDT

Originally Posted By 3rdtk:

Originally Posted By sysop:

Originally Posted By Reload_em:
The only thing that it looked like it might improve is accuracy, with the front sight much further out you would have a better sight radius. I would think that the handguards being longer would hold in more heat



Indeed the longer handguards on the carbine barrel help dissipate the heat from the barrel. Oh hey look at that! It's a Dissipator...........



Since we all know that heat rises, the only way that the so called "dissipater" can get rid of heat, is to only shoot into the air. It is about the hottest overheating gun out there.
Jack



OKay, from the Bushmaster Catalog, "the rifle length handguards offer greater heat dissipation (hence the name)." I would have to assume that they researched this a little bit before they made the claim.

@Szurgot

Correct but the difference would be subtle beyond being noticable unless you have spent a very very long time shooting AR-15's.

Link Posted: 8/8/2005 6:05:28 PM EDT
I could see a low profile gas block holding less and shedding more heat then a standard sight gas block. I also like the benefit of having less area to burn you, and more area to grab the gun. The longer sight radius is another notable benefit.

I'm a Dissy fan, but I never really worried about it's heat factors.
Link Posted: 8/8/2005 6:09:03 PM EDT
FWIW, chopping a 20" barrel to 16" is a no brainer. It's not rocket science and it works very nicely. The gov't profile barrels I have chopped make for an extremely light setup, even with a DD rail system. If I were going to get a Dissy, I'd contact one of the custom shops and have a 20" barrel chopped. YMMV.
Link Posted: 8/8/2005 6:11:15 PM EDT
[Last Edit: 8/8/2005 6:29:39 PM EDT by sysop]

Originally Posted By olds442tyguy:
I could see a low profile gas block holding less and shedding more heat then a standard sight gas block. I also like the benefit of having less area to burn you, and more area to grab the gun. The longer sight radius is another notable benefit.

I'm a Dissy fan, but I never really worried about it's heat factors.



There is that.

+ they are just dead sexy looking with the SP1 handguards:

Link Posted: 8/8/2005 6:22:21 PM EDT
Nice!!!! How can anyone not like the Dissy/SP1 twist.

Link Posted: 8/8/2005 6:32:16 PM EDT
I'm glad sysop changed that from dad sexy to dead sexy.

HS1
Link Posted: 8/8/2005 6:34:37 PM EDT

Originally Posted By HighStrung1:
I'm glad sysop changed that from dad sexy to dead sexy.

HS1



Yes well, me too. Sometimes my fingers don't type what I tell'em too.
Link Posted: 8/8/2005 6:39:07 PM EDT


OKay, from the Bushmaster Catalog, "the rifle length handguards offer greater heat dissipation (hence the name)." I would have to assume that they researched this a little bit before they made the claim.

@Szurgot

OK, since we all know that air and water are the two must accepted cooling factors, have them explain what is the majic they use, since the weapon can't breath from the lack of air circulation. I know that nothing about their claim, holds water! Just advertising BS about cooling, and just the opposit from personal knowledge, and common sense to understand why.
Cars get real hot on a summer day, untill the windows are opened for circulation. Maybe they have a fan hidden in there now, to blow the overheated air out?
Jack
Link Posted: 8/8/2005 6:50:06 PM EDT
Link Posted: 8/8/2005 7:14:06 PM EDT

Originally Posted By 3rdtk:

OKay, from the Bushmaster Catalog, "the rifle length handguards offer greater heat dissipation (hence the name)." I would have to assume that they researched this a little bit before they made the claim.

@Szurgot

OK, since we all know that air and water are the two must accepted cooling factors, have them explain what is the majic they use, since the weapon can't breath from the lack of air circulation. I know that nothing about their claim, holds water! Just advertising BS about cooling, and just the opposit from personal knowledge, and common sense to understand why.
Cars get real hot on a summer day, untill the windows are opened for circulation. Maybe they have a fan hidden in there now, to blow the overheated air out?
Jack



Ok, if you insist. The barrel on a Dissipator is still exposed to air via the vent holes in the forearm but the handguards are also lined with heat shields that absorbe heat, they are 4"s longer, they are also exposed to air. Ergo the full length forearms absorb and dissipate more heat on the 16" barrel.

After shooting and owning AR-15's for over 17 years I find your your claim that the Dissipator is, "about the hottest overheating gun out there." to be false.

The Dissipator may not dissipate heat faster than a standard 20" AR, but company will not make a statement in their catalog like "the rifle length handguards offer greater heat dissipation (hence the name)." unless they can back it up. They tend to have to provide data that proves such claims here in the USA. I am sure the lawyers at Bushmaster analyzed this claim, based on research done by the Bushmaster engineers and felt safe allowing it to be published in the catalog.

The Dissipator most certainly does not over heat or run hotter than a standard AR-15 Carbine. The Dissipator is more accurate at longer ranges using Iron Sights due to it's extended sight radius.

If you have more questions call Bushmaster. I'm sure they'd be happy to answer all your highly technical questions about how heat rises and stuff.


Link Posted: 8/8/2005 7:24:35 PM EDT

Originally Posted By sysop:

Originally Posted By olds442tyguy:
I could see a low profile gas block holding less and shedding more heat then a standard sight gas block. I also like the benefit of having less area to burn you, and more area to grab the gun. The longer sight radius is another notable benefit.

I'm a Dissy fan, but I never really worried about it's heat factors.



There is that.

+ they are just dead sexy looking with the SP1 handguards:
img319.imageshack.us/img319/3237/dissipators12rs.th.jpg



Not without the straight Delta rings!
Link Posted: 8/8/2005 7:40:49 PM EDT

Originally Posted By sysop:

Originally Posted By 3rdtk:

OKay, from the Bushmaster Catalog, "the rifle length handguards offer greater heat dissipation (hence the name)." I would have to assume that they researched this a little bit before they made the claim.

@Szurgot

OK, since we all know that air and water are the two must accepted cooling factors, have them explain what is the majic they use, since the weapon can't breath from the lack of air circulation. I know that nothing about their claim, holds water! Just advertising BS about cooling, and just the opposit from personal knowledge, and common sense to understand why.
Cars get real hot on a summer day, untill the windows are opened for circulation. Maybe they have a fan hidden in there now, to blow the overheated air out?
Jack

Ok, if you insist. The barrel on a Dissipator is still exposed to air via the vent holes in the forearm but the handguards are also lined with heat shields that absorbe heat, they are 4"s longer, they are also exposed to air. Ergo the full length forearms absorb and dissipate more heat on the 16" barrel.
After shooting and owning AR-15's for over 17 years I find your your claim that the Dissipator is, "about the hottest overheating gun out there." to be false.

The Dissipator may not dissipate heat faster than a standard 20" AR, but company will not make a statement in their catalog like "the rifle length handguards offer greater heat dissipation (hence the name)." unless they can back it up. They tend to have to provide data that proves such claims here in the USA. I am sure the lawyers at Bushmaster analyzed this claim, based on research done by the Bushmaster engineers and felt safe allowing it to be published in the catalog.

The Dissipator most certainly does not over heat or run hotter than a standard AR-15 Carbine. The Dissipator is more accurate at longer ranges using Iron Sights due to it's extended sight radius.

If you have more questions call Bushmaster. I'm sure they'd be happy to answer all your highly technical questions about how heat rises and stuff.





I am going to stir the shit

The part in red sounds to me like because the HGs are NOT HEATSINKS
Link Posted: 8/8/2005 7:48:55 PM EDT

Originally Posted By luckypunk:

I am going to stir the shit

The part in red sounds to me like because the HGs are NOT HEATSINKS



Ok and the metal liner in the handguards are?.................
Link Posted: 8/8/2005 7:49:31 PM EDT
Personally, I think maybe you're all thinking to much into it. My understanding of it is to dissipate heat away from the hands, not the gun itself.
Link Posted: 8/8/2005 7:52:56 PM EDT
[Last Edit: 8/8/2005 7:54:13 PM EDT by olds442tyguy]

Originally Posted By sysop:

Originally Posted By luckypunk:

I am going to stir the shit

The part in red sounds to me like because the HGs are NOT HEATSINKS



Ok and the metal liner in the handguards are?.................


They're actually called heat shields. Aluminum does in fact soak up heat, but it would be significantly less than the barrel's temperature, and would lose that heat alot faster than the barrel itself.

So in a way, it's possible they serve as both heat shields, and heat dissipators in cool down time.
Link Posted: 8/8/2005 7:56:05 PM EDT

Originally Posted By sysop:

Originally Posted By luckypunk:

I am going to stir the shit

The part in red sounds to me like because the HGs are NOT HEATSINKS



Ok and the metal liner in the handguards are?...........Not in contact with the barrel = no conduction = not a heatsink......




I think olds442tyguy has it right because the receiver end of the HGs have no vent holes to vent heat onto your hand, right?
Link Posted: 8/8/2005 7:58:03 PM EDT
[Last Edit: 8/8/2005 7:59:16 PM EDT by olds442tyguy]
Actually, I believe they are still vented the whole way. I'm not up on my standard rifle length handguard knowledge though. During shooting, the aluminum rifle length handguards and heat shields will keep heat away from the hands though, but will aid in cool down when not being shot.
Link Posted: 8/9/2005 4:30:24 AM EDT
Grab your carbine. Dump some 30 rounders, then using your bare hand, grab the barrel.

Do the same with a Dissipator, but instead of grabbing the barrel, grab the handguards.

Then ask yourself the following, "With respect to my hand, which design dissipates heat better?"
Link Posted: 8/9/2005 4:58:54 AM EDT

Originally Posted By jmart:
Grab your carbine. Dump some 30 rounders, then using your bare hand, grab the barrel.

Do the same with a Dissipator, but instead of grabbing the barrel, grab the handguards.

Then ask yourself the following, "With respect to my hand, which design dissipates heat better?"




[safety tip] professional shooters only, do not attempt [/safety tip]
Link Posted: 8/9/2005 6:06:53 AM EDT

Originally Posted By jmart:
Grab your carbine. Dump some 30 rounders, then using your bare hand, grab the barrel.

Do the same with a Dissipator, but instead of grabbing the barrel, grab the handguards.

Then ask yourself the following, "With respect to my hand, which design dissipates heat better?"



Do the same thing with a 20" A2 rifle and a dissipator. Grab the handguard. NO DIFFERENCE
Link Posted: 8/9/2005 12:49:09 PM EDT
Theoretically, a Dissy does in fact have better heat to hand properties. I myself have not tested it, but it seems fairly simple to understand.

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