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Posted: 9/28/2003 9:55:36 AM EDT
I currently have a pre-ban Colt HBAR and want to put a lighter, shorter upper on it. The Dissipator idea, especially with a lighter weight barrel seems like a good idea.

So, does the Dissy use a normal 20" gas system (length and port size)? Is it basically just a cut 20" that has beeen recrowned and rethreaded (for pre-ban configuration)? If so, could I just pick up a 20" upper, and have a smith chop and rethread it to 16-18"? All I would need is a source for a lighter weight 20" barrel/upper.
Link Posted: 9/28/2003 11:50:15 AM EDT
The std dissipator is a carbine length gas tube in a 16in barrel with a sight block and handguard cap up front. You could chop a 20" but ADCO is the only place that is reputable and will chop chrome lining. The std rifle tube can be used but the port has to be opened to .090-.1inch to get it to work. Length is 16inches [b]18inches can be done without enlarging the port.[/b] 16in is better for suppressors (less weight out front and 18in is probably the best length for velocity vs length with Ar's so the choice is yours.
Link Posted: 9/28/2003 1:46:15 PM EDT
Originally Posted By Green0: You could chop a 20" but ADCO is the only place that is reputable and will chop chrome lining.
View Quote
Kurt's Kustom is also 'reputable' and he's been making conversion like this from 20" barrels for some time now.
Link Posted: 9/28/2003 2:12:13 PM EDT
[Last Edit: 9/28/2003 2:12:47 PM EDT by Boom_Stick]
Here's what I did with my M4 barrel. [img]http://www.hunt101.com/img/061437.jpg[/img]
Link Posted: 10/4/2003 6:36:06 AM EDT
[url="http://www.hunt101.com/?p=62459&c=500&z=1"][img]http://www.hunt101.com/img/062459.jpg[/img][/url] -- Chuck
Link Posted: 10/4/2003 6:43:30 AM EDT
Thanks for the info. I'll check out ADCO and KKF for prices. I think I will go for a cut down 20". Now, I'll I need to do is find a non heavy profile 20" with a relatively fast twist rate 1 in 8-9". Any ideas on sources? Chuck. what exactly do you have there? Is that a lightweight 20" that was cut to 16", or is it a CAR barrel?
Link Posted: 10/4/2003 9:37:51 AM EDT
Originally Posted By Green0: The std dissipator is a carbine length gas tube in a 16in barrel with a sight block and handguard cap up front. You could chop a 20" but ADCO is the only place that is reputable and will chop chrome lining. The std rifle tube can be used but the port has to be opened to .090-.1inch to get it to work. Length is 16inches [b]18inches can be done without enlarging the port.[/b] 16in is better for suppressors (less weight out front and 18in is probably the best length for velocity vs length with Ar's so the choice is yours.
View Quote
I have built 4 "dissipators" and have yet to open up a gas port in a Colt barrel. They all work, the one I have has worked for 10 years. Scott
Link Posted: 10/4/2003 9:47:24 AM EDT
Just buy the Bushmaster Dissy barrel. It comes with the gas tube and the hand Guards if you want. I have also built 4 for other people from their kits. I have one which I am floating with the BMAS Hand Guard and BMAS 3 rail gas block with detachable front sight. I usd the full length BMAS. Mine is built on an eagle arms lower with a Bushy National Match Trigger. I used the ACE skeleton stock for it. I used the heavy barrel kit for mine. 3 of the 4 fits I built used fluted barrels. Only one and mine were Bushmaster barrels. I forget who the other ones were. Will post a picture when I get done.
Link Posted: 10/4/2003 9:52:12 AM EDT
Has anybody had KKF cut down a 20" to a 16" Dissy clone? Does it cycle reliably? It would be the lightest setup since you lose the second gas block/sight tower.
Link Posted: 10/4/2003 10:32:38 AM EDT
In my opinion it is easier to just get the barrel kit and save the money it would cost to send it out and cut a perfectly good 20" barrel. Save the money for a scope, trigger or a free float system. The amount of weight saved is miniscule. You can get the milled front sight base if you want also. Now if you are going to use the regular handguard you need the very first block. I do understand that if you take the front block off you have the machined surface to contend with. I can't wait till I finish my BMAS system. I will post some pictures. But from the pictures I see so far posted mine is like a economy car. I really like the FIRSH or ARMS SIR system. That will be my next build after my Benchrest AR15 setup.
Link Posted: 10/11/2003 8:46:03 PM EDT
I had KKF cut down a Colt 1 in 7" chrome lined 20" HBAR to 16", turn it down to A2 Specs under the handguards and rethread and reinstall A2 FH and put it back on the original Colt A2 Upper. He calls it a Lightweight Kurtsgewehr. I later added a Colt old style fiberite collapsible stock. I love mine and it functions great. KKF only charges about a hundred bucks to do it.
Link Posted: 10/11/2003 9:44:18 PM EDT
yeah kurt just cut my 20" colt 1/7 HBAR (turned down to gubmint profile) to 16.5" and i am looking forward to getting it back and out to the range.
Link Posted: 10/12/2003 8:38:48 AM EDT
I think it is an awesome combination. I think you will love it.
Link Posted: 10/19/2003 7:30:15 AM EDT
[Last Edit: 10/19/2003 8:26:37 AM EDT by edpmedic]
How much did it cost to have it done? [url]http://photos.ar15.com/WS_Content/ImageGallery/ImageDetail.asp?iDBLoc=0&iGalleryUnq=1120&iNumColumns=4&sSort=&iTtlNumItems=1&iCategoryUnq=0&iNumPerPage=20&iImageUnq=18837&[/url] This is the one I just built. Will add better pictures later. Bushmaster Dissy upper barrel kit Eagle Arms lower and National Match trigger BMAS Handguard with the 3 rail gas block and sight. ACE Stock.
Link Posted: 10/19/2003 8:10:20 AM EDT
[Last Edit: 10/19/2003 8:12:11 AM EDT by ltmdpd]
I ordered an A3 Dissipator from Bushmaster with a fluted barrel and free-floating four-rail handguard. Also has a two-stage trigger. Have an ACOG TA11D on it and its GREAT! Also put the three-rail fold down front sight on it. KAC 600 BUIS. While I have several AR's, this one quickly jumped to the top of my "If I only had one" list. You might want to consider the fluted barrel and free-float handguard, whether putting together yourself or just an upper.
Link Posted: 10/19/2003 8:35:40 AM EDT
The next one I build gets a fluted barrel. I also think I will build it with the Arms S.I.R System. The one I just built still needs the Mini Y Comp installed. When I put my ACOG on the flash is a killer to my eye sight.
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