AR15 16" upper question

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twoblink

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I began by assuming that increased sight radius = increased accuracy.

So, my question is: does anybody have first hand experience that this:
pura2b16d.jpg


Will shoot more accurately than this:
pura2b16.jpg


Also, I assume the faster heat dissipation helps also.. But I'm wondering by how much..

Also, anybody know just how much additional sight radius you do gain??
 
twoblink, the Dissy has the same sight radius as the issue 20" A2 rifle (19.75"). I've found that it does help accuracy if you are using the iron sights. With optics, the point is moot; but without them, you gain 5.25" over the carbine sight radius.

I don't know that it makes the barrel cool any faster (and kind of doubt it even); but having a lot more handguard to heat up, it does take a lot longer to get uncomfortable to hold compared to the shorter carbine handguards.

Most Dissy's use a second gas block under the handguard at the carbine gas block location, so they weigh a little more than an equivalent 16" carbine barrel would. Kurt's Kustom has been having luck with what he calls his Kurtzgewehr - a 20" rifle cut down to 16" with a single gas port that has been opened up for reliable functioning. All of the production offerings I am aware of use the two-gas block method though.
 
Well they both use the same barrel and the same gas system so there really shouldnt be any difference in accuracy between them. Now in theory the longer sight radius can make the dissapator more SHOOTABLE but that depends on the user anyways. Neither is more inherently accurate than the other though.

Personally, if i were you id by the one that i liked the look of. There are basically the same rifle in different clothes. Both very fine choices.
 
My personal preference between the two (right now) is between the two :confused:

I prefer the "mid-length" handguards that Rock River Arms offers as an option (The rifle pictured in the middle), or that Armalite offers as their standard.

rcara2.gif


The front sight AND the gas tube are 2" farther out than the carbine, giving (theoritically) a softer shooting and more reliable rifle because of the longer gas tube, and slightly more sight radius for slightly more accurate aiming potential with iron sights.

There's also a little less weight forward since you don't need 2 gas blocks, and if you choose to have it turned to A2 profile or fluted, you don't have to leave the barrel untouched in the middle for the "hidden" gas block.
 
The Dissy has a "second" gasblock because the front sight tower has been moved forward. The Dissy uses a gasblock over the original gas port on the 16" barrel-the gas tube does attach to the sight tower on a Dissy.

I tend to shoot my Dissy better than a standard CAR configuration due to the increased sight radius. However, the Dissy is muzzle heavy in standard configuration. KKF does offer a service to turn down/flute a Dissy barrrel to lighten things up a bit.
 
Can someone explain to me, why the Dissy's have a second gas block?
Click to expand...
Only the first gas block is attached to the gas tube.
There is only one hole in the barrel to bleed gas.
The second gas block is there so you have a front sight, and is the front mounting point for the handguard.
 
Now I know you are not thinking of buying an AR-15. I mean, GASP :what: It's not in .308 for gawd sakes. What is the world coming too.....cats and dogs living together, Twoblink looking at something other than .308 MASS HYSTERIA!!!!!

There is the AR-10 ya know. :D

Just kidding. Enjoy. You can now go back to your intellegent conversing. Move along, nothing to see here.

Chris
 
i think twoblink may be asking why this arrangment is necessary. The idea is that with the AR15 gas system the gasport has to be about 4 inches from the muzzle in order to cycle properly. It has something to do with the gas pressure or somesuch being less closer to the muzzle. This is why every ar15 varient has that length of barrell going out so far past the front sight. The dissipator solves this issue by placing a gasblock under the handguard in the same place that it would be on an M4gery. And placing an ADDITIONAL frontsight/gasblock at the end of the barell that just functions as a front sight.
 
Cslinger..

One comment..

"Girlfriend Logistics" (Trademark Pending)

:D

Also, I actually own 2 AR15 lowers (Bushy's) those were actually my first 2 gun purchases.. Before I "saw the light".

Also, I haven't filled the CQB roll.. That's the problem. I like the M1Carbines, but the AR15's might fill that roll a bit better, and might be what the gf will end up with..

Or a 16" M1A???!!! :what:
 
I looked at both before buying my Bushmaster Shorty. I wasn't planning on using the 16" barrel for anything more than 200 (really 100) yards anyway as my plans in the future include a 24" flat top upper for those purposes.

I didn't care for the Dissapator after handling it. It felt nose heavy to me. The shorty seems much handier, and I just don't like the looks of the Dissy. As to heat dissapation? I think that is a sales gimic, however with no exposed barrel, burning yourself after several quick shots is not going to happen.
 
I like my Dissy very much. In my hands, it's more accurate than the Shorty.
I agree that the heat issue, which ironically is what give the Dissy its name, is a gimmick. The added sight radius issue, however, is real.

As far as appearance, I happen to like the Dissy better than the Shorty. I do like the intermediate that Onslaught posted also.
 
baddadbrad, did you play with the heavy barrel? I know they make some M4 profiled barrels for them now too.
 
As far as the heat issue, I think not burning yourself is the main point, actual amount of heat that is carried away might be more, but doesn't make one bit of difference, you still get burned when you touch it.

My friend's got a shorty and a dissy.. and I shoot the dissy a bit better (from an ergonomic point of view) not necessarly an accuracy point of view.
 
The longer sight radius will yield more accuracy, all other things being equal. The previous poster is correct, the Dissy direct from Bushmaster is way too heavy. I had KKF turn and flut mine. Build it on an A1 upper, and you have an outstanding little carbine.
 
I just received my RRA Mid-Length. A great improvement on looks over the short grip that leaves the long barrel poking out like a pencil past the front sight.
I vote for the RRA mid-length!
 
no bayonet mounting on a dissy
Click to expand...

Im pretty sure that you cant mount one of mist M4geries either. Arent those handguards originally intended for 14.5" barrels? There may be too much barrel between the lug and and the flashhider anyways to mount a bayonet.
 
The RRA mid-length doesn't seem any lighter than the Bushy Dissy though...
Click to expand...
Nope...

BUT, if you're interested in a bit of custom work, a mid-length can be made lighter than a Dissy can be made. Turning and/or fluting both barrels will yield slightly less weight on the mid-length because you can do a full flute or turning under the HG, and there's only one gas block.

Either one's a winner though.

FWIW, I understand that the "new" 6.8mm rifle that our military is devoping is a mid-length also.

I have no first hand experience (yet) but I've read others who say that the mid-length gas tube makes for slightly slower recoil impulse than the carbine gas tube. I've decided that I may KEEP my 14.5" upper assy, so I'll be able to let you guys know for sure.... at some point..... after I can afford another upper and bolt for the new barrel..... once it gets back from KKF ;)
 
AFAIK, Rock River is the only ones making it. I saw in ad in SGN where someone else is selling a mid length, but it might be RRA's parts. Remember the DeWalt AR-15 post? The company selling the colored furniture also offers the midlengths in colors too.
 
In addition to the longer iron sight radius. For offhand shooting, the longer forend works better for me. YMMV
 
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