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CMMG 300Blk Barrel


Robocop1051

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I think Bushmaster started the "Dissipator" style. Now others, like BCM, are doing the same thing.

Originally they were 16" carbine length barrels with low-pro gas blocks under a handguard, and a rifle length A2 front sight mounted to hold the handguard in place.

Now they are just any length barrel, with a gas block length shorter than the front sight length. I've also seen pistol/mid length, Car/Mid length, Mid/Rifle.

2243b.jpg

http://www.model1sales.com/index.cfm?fuseaction=category.display&category_id=368

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So a dissipater front sight is just an A2 front sight mounted at the front of a barrel with a low pro gas block mounted seperately, further back? Someone told me that a dissipater style AR was a rifle with a railed handguard that completely covered the barrel. I'm going to have to work harder on keeping up on the currant terminology.

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If CMMG makes a decent enough barrel, I'm in. Their price is attractive, but I can't imagine much quality from that low of a price tag. Especially when the Noveske barrel is more than double the cost.

I'm thinking about maybe a carbine length Osprey piston kit, wrap a rifle length MOE handguard around it, then come up with something fancy for the front sight. Maybe even a BABC for fun?!?

It'd look similar to this...

k281474_Dissipator%20Radical%20Dude.jpg

(I love tough chick's!)

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Anyone know what the ID is on the A2 front sight? It would seem that it ahould be pretty easy to set up any barrel for this setup as long as the OD of the barrel matched the ID of the A2 sight or was close enough so you could bore the sight out, or use bushings if it was bigger than the barrel.

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The inner diameter of an A2 front sight block should be either .625 or .750... A shim or bore-up would be the easy enough. The problem would be the taper-pin holes... and I have ZERO interest in trying that.

If the barrel isn't made to fit a rifle length front sight, I actually plan to use a "clamp-on" style PRI .750 GB (I have an extra one laying around)... If I can't tighten it down tight enough as it is, then I can modify it for adjustments.

Most of the regular diameter barrels I have looked at are .700-.710 from the gasblock location to the bore. Fitting shouldn't be an issue.

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I hadn't taken the pins into account. As you say, boring the sight out from .625" to .710" wouldnt be hard, and going in with an endmill and then reaming the holes to take pins would also be doable, but once you do, your stuck with that setup, unless you don't mind having the two crescent shaped grooves on the bottom of your barrel showing if you ever decided to remove it and go back to a set of BUIS on your upper/rail. It does look good though. I was looking at some sights online, and Vltor has a flip up front sight that comes out of a short pic rail section that bolts to the barrel, of course it doesn't have the classic look of an A2 front sight.

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I just took a closer look at the two pics you posted. In the first one from model 1 Sales, I see that the "Dissipater" barrels that they have pictured, have the front handguard retainer, but I'm not familiar with the Magpul MOE handguard, does that also make use of the front handguard retainer? What I'm wondering is, would there be any reason, other than looks, for mounting an A2 front sight to your barrel if you intended to use a freefloat handguard and weren't planning to make use of the factory style front handguard retainer? does the A2 front sight, mounted to the barrel, offer any advantages over a non folding front sight mounted to the front of an extended ff rail?

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@Jgun,

The Dissy barrel is strictly to have a longer sight radius when using a regular handguard (like the MOE) on a carbine length barrel. Using a FF on a Dissy would be a little silly in my book as you could extend the FF and get the same results, as you pointed out.

@6132expert,

That is the post I've been waiting to hear! Thank you.

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You can use the clamp-on Armalite front sight base on the barrel.  That's what I picked up for my .45 AR Dissy build.  The barrel is .750 at the traditional gas block mounting location, and very slightly steps down in front of that.  The .750 Armalite clamp-on definitely had the range to clamp down very, very securely to the barrel.  <thumbsup>  It was incredibly cheap through DSG Arms, with the MIL discount.  Forty-something. 

100_0192.jpg

100_0197.jpg

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Be advised - the Armalite clamp-on comes "unloaded."  You'll need to pick up a front sight post, spring and detent.  It does come with the allen bolts to clamp it on.  <thumbsup>

You will need a 16" barrel if you intend to run rifle-length handguards.  A 14.5" will be too short. 

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