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Old 03-03-2013, 12:23 AM   #21
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Read the fine print. Those are "mock" dissipators. Not that there's anything wrong with that.
Once upon a time, a "dissipator" AR was created by taking a 20" rifle-length gas system upper and cutting the barrel down to 16". This allowed the shooter to keep the long sight radius of a rifle for accuracy, but keep the carbine length barrel for maneuverability. The proximity of the gas port to the muzzle, however, played havoc with timing and made reliability a hit or miss proposition. Advances in AR technology have produced reliable carbine and mid-length gas systems, that can be hidden using low-profile gas blocks. This allows for a front sight base to be pinned in the rifle position for the longer sight radius without the worry of the unorthodox gas port location affecting operation. We use the term "mock" to differentiate our dissipator from a cut-down rifle length version.


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Old 03-03-2013, 12:26 AM   #22
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Never mind. PSA has dissy uppers in stock so I ordered one.
I'd been watching PSA and Del-ton waiting for a dissipator too, and yesterday they popped up so I grabbed one too. I have a Bushmaster lower with Magpul hardware and MP gear just waiting for it! I see today their back to "sold out" status.


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Old 03-03-2013, 12:49 AM   #23
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Originally Posted by Westy

I'd been watching PSA and Del-ton waiting for a dissipator too, and yesterday they popped up so I grabbed one too. I have a Bushmaster lower with Magpul hardware and MP gear just waiting for it! I see today their back to "sold out" status.
Right on. Gonna put black MOE handguards on it and probably a Troy flip up rear. Not sure what optic yet.
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Old 03-03-2013, 01:12 AM   #24
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Here are some for your comparison. But of course the optimal one to have, and my grab-n-go, is a true middy like my lovely BCM...

barrels-corrected-compressed.jpg   bravo-company-ar.jpg  
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Old 03-03-2013, 02:05 AM   #25
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HockaLouis- Explain please!

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Old 03-03-2013, 03:16 AM   #26
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HockaLouis- Explain please!
I second that motion.
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Old 03-03-2013, 04:55 PM   #27
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What Hocka was referring to is that the midlength gas system has devolved to become a more optimized system for 16" carbine barrels.

When civilian carbines were made in the AR platform they were forced to use 16" barrels for legality, while the original carbines developed for the military had shorter barrels.

When the gas port is moved closer to the chamber, as in the carbine ARs gas pressure is higher at the time it is vented back to the bolt carrier. This means it will have more force applied to it. This improves reliability in a short barrel because that short barrel has less bore past the gas port to keep gas pushing rearward, this is known as dwell time. So, if we look at the original rifle length AR as being the optimum for gas pressure and dwell time as a comparison we can see that a 16" carbine system will have high pressure and long dwell time which can be kind of heavy on wear of the parts over time, cause bolt bounce, etc. from over gassing the system. The mid length system moves the gas port away from the chamber resulting in venting the gas back as it has dropped in pressure a bit, but still with the exact dwell time, or remaining barrel lengthy from the gas port to the muzzle. This gives better reliability than having low pressure and short dwell time, which can be unreliable in cold weather or with light loads.

Rifle lengthy gas systems on 16" barrels can be made more reliable by opening the gas port up and using lighter buffers. Carbine length systems can be made to cycle more gently by using heavy buffers and bolt carriers.

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Old 03-04-2013, 02:58 AM   #28
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Quote:
Originally Posted by Westy View Post
Once upon a time, a "dissipator" AR was created by taking a 20" rifle-length gas system upper and cutting the barrel down to 16". This allowed the shooter to keep the long sight radius of a rifle for accuracy, but keep the carbine length barrel for maneuverability. The proximity of the gas port to the muzzle, however, played havoc with timing and made reliability a hit or miss proposition. Advances in AR technology have produced reliable carbine and mid-length gas systems, that can be hidden using low-profile gas blocks. This allows for a front sight base to be pinned in the rifle position for the longer sight radius without the worry of the unorthodox gas port location affecting operation. We use the term "mock" to differentiate our dissipator from a cut-down rifle length version.
Exactly.

To each his own. But I don't see the point in a "mock" dissipator. Longer sights? Sure, then everybody tricks them with optics. What's the point? Get a middy.

I just don't see the point of a fake dissy. That's just me.
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Old 03-07-2013, 06:56 PM   #29
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I want an optic for this rifle but I don't know what to go with. I have an eotech already.



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