Want a mid-length gas system Dissipator. Who makes mid uppers?


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TOU
August 17, 2007, 03:06 AM
Who all makes mid-length gas system uppers? I want to probably build a Dissipator style AR in the near future. I would consider Bushmaster, but I do not believe Bushmaster makes them in this version or with the options I want.

Basically I want a 16" chrome lined lighter barrel with a mid-length gas system on an A3 upper without any fixed front sites....rail instead. (But want a carrying handle. Would love to buy it in a factory configuration but am under the impression this is impossible. So, will probably by a M4 Stag lower and am trying to figure out who's upper? So....recommendations?

Thx,

TOU

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BamBam-31
August 17, 2007, 05:22 AM
Did you check Rock River?

www.rockriverarms.com

gdvan01
August 17, 2007, 05:30 AM
ar15.com

DMK
August 17, 2007, 08:30 AM
Bushmaster doesn't sell a Midlength and RockRiver doesn't sell a Dissipator.

www.cmmginc.com has 'em.

Shear_stress
August 17, 2007, 08:32 AM
Lots of folks make mid-length uppers. I bought mine from RRA. CMMG's M10M upper has a 16" barrel, mid-length gas system and with the option of a railed gas block instead of a front sight.

As a side note, I am not sure if I understand your use of the term "dissipator". The Bushmaster Dissipator had a regular carbine-length gas system, but with the front sight pushed forward and full-length handguards installed. There's nothing mid-length about the gas system.

benEzra
August 17, 2007, 10:50 AM
Having no front sight makes it not exactly a Dissipator. As Shear_stress mentioned, a Dissipator is a carbine-length gas system with a separate front sight block placed way forward on the barrel, so that it will take full-length handguards.

I think the closest thing to what you want would be to start with something like the midlength A4 config below:

http://www.rockriverarms.com/images/mida2407.gif
http://www.rockriverarms.com/item-detail.cfm?ID=AR1294X&storeid=1&image=mida2407.gif&CFID=1836187&CFTOKEN=75907749

and then under the options, select "Gas Block and Detachable Front Sight." That way, you can remove the front sight completely, and (if you wish) replace it with a fold-down FS instead. I'm not sure you can get a lightweight barrel profile from RRA, though.

Regarding the carry handle, are you wanting something on which to mount an optic, like RRA's "Tactical Carry Handle"? An A4 style carry handle with no front sight would seem to be the worst of both worlds; the regular carry handle gets in the way of mounting an optic, and lack of a front sight makes the rear sight useless.

strat81
August 17, 2007, 10:56 AM
For those not "In the Know" Dissipator style AR-15s have rifle length handguards and a 16" barrel. CMMG is the only one I know that makes Dissipator-style rifles in carbine, mid , and rifle length gas systems.

DMK
August 17, 2007, 11:36 AM
You could make a "pseudo Dissipator" by putting a rifle length free float handguard or tube over a carbine or midlength gasblock. However, you need a very small gasblock to fit the handguard over it.

nalioth
August 17, 2007, 11:41 AM
I'm surprised you guys aren't looking at http://www.model1sales.com or http://www.m-aparts.com/

Sry0fcr
August 17, 2007, 12:09 PM
Why a midlength instead of rifle length gas system? You're going to have to use a lo profile gas block anyway, might as well get the better gas system...

TOU
August 17, 2007, 12:46 PM
Came across the following from Bartholomew Roberts

Well, by virtue of going with a 16" midlength gas system you are looking at Armalite, RRA, Bravo Co., CMMG, or Sabre Defence. Those are the five factory manufacturers I know of that produce a midlength, though there are a ton of custom AR builders who can assemble a midlength in addition to that. (http://www.thehighroad.org/showpost.php?p=3562002&postcount=2)

So I guess that is a start as to where to get an upper.

DMK wrote:

Bushmaster doesn't sell a Midlength and RockRiver doesn't sell a Dissipator.

www.cmmginc.com has 'em.

Agreed, I noted this which is why I have resigned myself that to get what I really want, that I'm going to have to build my first AR myself. (never owned one before) I just thought I would try to limit what I HAD to do this first time...but like everyone, I'm on a budget. Which means, CMMG seems to have nice stuff, but they do tend to be significantly higher in cost, comparatively speaking, than others. To get what I want though, I may just have to ante up I guess. I haven't fully done the math though.

I saw a few post about taking a rifle length system and cutting down the barrel to a Dissipator set up, but in other post people allude to shorter barrels with a rifle length system is bad. Can you please also bring me up to speed on these thoughts.

This picture on the front page of the CMMG sight looks like it may be quite close to what I would like.

Shear_stress, I visited CMMG's site....

http://cmmginc.secure-mall.com/shop/?shop=1&cart=753661&cat=61&noCookiePassThrough=Y&

...but in my ignorance I didn't see the "M10M" designation. I should also mention I would like a 1:9 twist and not a 1:12. As to my use of the term "dissipator"; yes I understand technically that the Bushmaster Dissipator had a regular carbine-length gas system, but with the front sight pushed forward and full-length hand guards installed and also that there's nothing mid-length about the gas system....good points. I should qualify it in that I want that style but want the Dissipator that BM should have built. One with full length rails or at least hand guards, mid-length system, lighter 1:9 chrome barrel and I personally want with removable FULL-Length front and rear flip sights. So in the end, it will be the long sighted, long hand guards Dissipator style rifle while having a few upgrades to my taste. The question is am I going to be able to do this for a total of $850? With the fr & Rr flip up sights I am starting to doubt it.

DMK wrote:

You could make a "pseudo Dissipator" by putting a rifle length free float hand-guard or tube over a carbine or midlength gasblock. However, you need a very small gasblock to fit the hand-guard over it.

DMK, I think that this may describe the closest to what I'm trying to get at. The one below that I found on AR15, may also be a good visual but not with the HB...lighter barrel instead.

http://i8.tinypic.com/4q6djwi.jpg

http://i18.tinypic.com/6399b3b.jpg

http://i17.tinypic.com/5x81352.jpg

http://i9.tinypic.com/4q6w3fa.jpg


Why a midlength instead of rifle length gas system? You're going to have to use a lo profile gas block anyway, might as well get the better gas system...


Good question (also see above) and hopefully, someone will help me answer this question. Thank you for your responses and I thank you in advance for your further input.

Cheers,

TOU

MrAcheson
August 17, 2007, 12:59 PM
Why a midlength instead of rifle length gas system? You're going to have to use a lo profile gas block anyway, might as well get the better gas system...Because if you have a 16" tube, rifle length isn't necessarily the "better gas system". Midlength is arguably the optimum gas system for a 16" barrel. With rifle you're gas port may be too close to the muzzle to get the pressure you want to cycle the action. With carbine you'll get more pressure than you need. Midlength is the happy medium.

nico
August 17, 2007, 01:22 PM
Based on other people's experiences, 17" seems to be the minimum barrel length for a reliable rifle-length gas system.

TOU
August 17, 2007, 01:34 PM
This was a pretty good read on gas systems.

http://www.thehighroad.org/showthread.php?t=199626

(BTW nico, I was kinda leaning toward Romney....hmmm)

TOU
August 17, 2007, 01:50 PM
One more picture I thought was worth reviewing. (Sorry for the size, I don't know how to make this site resize the picds.)

http://i19.tinypic.com/5yrbg45.jpg

Bartholomew Roberts
August 17, 2007, 02:10 PM
17" is as short as you want to go for reliable function with a rifle length gas system. Otherwise the dwell time is too short and you run into some of the same issues that plague the shorty ARs. You can make a 16" rifle length gas system run well, it just won't run as well as the 17" rifle or the 16" midlength.

If you are set on a 16" midlength, also consider a free float rail system with a 13.2" rail system. If you place a folding front sight on the front of the rail, this will give you the same sight radius as the rifle. You would need to use a lo-profile gas block (if you have a dremel and a sander, you can modify the A2 front sight base to lo-pro as well, if you have the time).

Otherwise, for a factory manufactured midlength Dissipator, you are looking at a CMMG.

Siderite
August 17, 2007, 02:31 PM
I think Shear_stress was right - you'd want the M10M upper from CMMG. To find it on their site, select "uppers" then "CMMG 5.56mm Carbine/Rifles Uppers" and scroll down about half way to "CMMG 16 M10M Upper".

Full description:
New 16" M10M upper. This upper is built around the M10 multi-role barrel with mid-length gas, rifle length handguards, rifle length sight radius and is complete with bolt, carrier and charging handle. CMMG semi auto bolt carriers have the shrouded firing pin to protect against hammer wear. Upper receivers are "T" marked and include extended feed ramp cuts. Features include medium contour barrel, 11 degree recessed target crown, triangle handguard cap, chrome-lined 5.56mm chamber and bore, 1/7 twist, parkerizing under F marked forged front sight base and magnetic particle testing on every barrel. When ordering with optional gas block, barrels will not be drilled for taper pins. Barrel is marked CMMG MPC 5.56 NATO 1/7.

It has a 1/7 twist, which is tighter than what you specify.

To get it to look like the one in post 15, you'd want the "Front Sight Base/Gas Block Option" to be one of the flip-front sights. The "Handguard Option" to be the "PRI Gen III Carbon Fiber Rifle Handguard" (I think the one you posted is actually the YHM Customizable Free Float Forearm System, but that isn't an option, but the PRI is the other round handguard with rail mounting slots - lighter, but more expensive). And then, since you said you wanted a detachable carry handle, "Rear Sight Option" set to that.

If you want to figure out what each of the options is/what it looks like, you'll have to google the individual manufacturers, ex: YHM forearms: http://www.yankeehillmachine.com/store/forearms.html

disclaimer: I have no association with CMMG; I've just ordered one upper from them, since they made it easiest to customize to my liking.

TOU
August 17, 2007, 03:01 PM
I found it now...I was going under the "light" section. Thank you.

I guess I may eyes bigger than my belly...or in this case my wallet. At $1163.40 shipped (from the CMMG calculator) to my door for just the upper alone....I may have to figure on something less for now. :o It's just kind of tough when I can buy an BM A3 Dissipator for $859, complete. :scrutiny: ...but it does not have the mid-length gas system. Thx so much for your all's input, I do appreciate it.

Back to the drawing board. :confused: ;)

nico
August 17, 2007, 03:55 PM
If you're looking at a model with the PRI handguard, a big part of that price is the handguard. I'd recommend starting out with a flat top midlength and changing the handguard and getting new front sight as funds permit.

A RRA A4 midlength upper with a chrome barrel is about $435 from Legal Transfers on ar15.com. I bought the same upper with a stainless barrel from him and have no complaints about the upper or his service.

$850 is a little optimistic if you want the complete gun with a full length handguard and front and rear flip-up sights, but it should be doable without spending too much more than that. You could also save a few bucks if you get a rail mounted front sight instead of buying an additional gas block.

If you keep an eye on the equipment exchange on ar15.com, you can save a decent amount of money.

TOU
August 17, 2007, 08:44 PM
I agree nico, $850 was very...too optimistic. I think the things like the floated hand guards are going to come later. Even so, with out those hand guards, it still pits in at nearly $900 for just the upper alone! I do have to think that for $850, I should be able to put something together with a mid-length gas system, no front sights in an A3 config...with chrome lined light weight barrel and carry handle.

You know...this whole dang thing would be solved if Bushmaster would just offer the Dissapator A2/A3's in a mid-length system. ;)

TOU
August 21, 2007, 02:46 PM
Okay here is where I am at....

A DPMS 16" chrome lined NEW in box FACTORY BUILT DPMS A2 Carbine AR-15 5.56mm rifles - $645*

http://www.dpmsinc.com/@ssets/images/firearms/large/5.56x45mm_carbine_a2.jpg

Or an Armalite A4 MIDLENGTH with front site and detachable carry handle, collapsable stock...slightly used but ANIB for $775.

http://www.armalite.com/images/large%20images/Rifles/15A4CBA2%20Large.jpg

Or the same MIDLENGTH Armalite rifle without carry handle or any sights but NEW for $850 (No scope but does have the mount included)

http://www.budsgunshop.com/catalog/images/11572.jpg

http://san1.atlanta.gbhinc.com/GB/078600000/78600793/pix329380031.jpg

Or Finally an A3 Bushmaster Dissipator that is NEW for $859. (HB and collabsible stock.)

I realize the DPMS is not midlength nor is it Dissipator style like I wanted but man that price is nice for a first AR on a budget and it is now.

Thoughts?

nico
August 22, 2007, 12:04 AM
I'd go with one of the Armalites. There's really no advantage of a carbine length gas system and a few disadvantages as compared to a midlength on a gun with a 16" barrel.

I would still suggest at least buying the upper and lower separately and looking around on arfcom. I bought an RRA midlength A4 upper w/ SS barrel, LMT rear sight, and Ameetec complete lower w/ collapsible stock and an H-buffer for a total of $780 shipped.

Since I bought my gun, the owner of Ameetec has shown himself to be a crook, so I'd recommend getting the lower from someone else.

Bartholomew Roberts
August 22, 2007, 12:40 AM
I like the Armalites best out of the choices you listed. The cost of the Armalite scope mount separately is about $123 IIRC, so the new Armalite with scope mount is probably a better value than the almost-new one if you plan to place a scope on it.

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