dissipators and rifle gas.

[peabody]

hello folks.

lookings at dissipator uppers on the web,

DPMS has a dissy, with rifle gas, wonder ? if they open the gas port up ?

had a carbine dissipator, also have a M4 carbine, but they cycle too fast and harsh,
since i picked up a middy gas barrel, i havent looked back since,

i'm going to try out , cutting an old M16 barrel, back to 17.5 inches, shouldn't haves any problems ?
i do have a 20'' service rifle, and just love the bloody thing, so soft n' smooth.
but a little long, hence: cutting back a 20 to 17.5 and trying that, with a 6-position stock..
whats your thoughts on that ?

peabody


p.s. im wanting another dissipator, cause everybody shoots mine !!

 

[PT1911]

I just bought the DPMS.... LOVE IT.. it is my favorite AR platform... not really sure why, but it is.

 

[peabody]

im glad you like it ! . altho ? i've looked at DPMS on their website, but they say nothings about the gas port.. that i can find ?

like you . thinking about it, im thinking rifle gas is the way to go. just use good ammo...
im not a high round shooter, but man ! i love my dissy, for hunting and banging around the farm , tractor/pickup gun.

im thinking of building one, like i said with a cutt down barrel, but ? might just order a upper from DPMS. and be done with it. whats the twist rate on yours ?

peabody

 

[Al LaVodka]

I've read the distance from the muzzle to the gas port is the issue that dictates the position of the gas block and not from the chamber to the gas port. Not sure I buy that as how do da bullet know? But the Carbine length system could be designed to work with different tolerances than the rifle. And a true middy also (which may cause less gas-cutting).

So, what's the real deal? It can't be that complicated!

FYI, I have experience with two (Carbine-length gas tube) Dissipators...

Al

 

[peabody]

just ... thinking on how best to start a build for another dissipator, for some unknown reason. i wants a dissy with rifle gas... why ? dunno ? i just do.

maybe someday put a DCM freefloater under those handguards.

the length of the dwell time, is the reason im thinking of just cutting this extra barrel to 17.5 , and go from there, i'll probly never notice the extra 1.5 inches of barrel.
but it just might make all the defferance in the world, for the rifle to cycle perfectly,
who knows ?

im just thinking outloud.
getting your inputt's.

peabody

 

[Tirod]

Gas system length per barrel:

14.5" M4 - carbine
16" - midlength
18" - intermediate
20" A2/4 - rifle


The amount of barrel from the gas block to the muzzle is fairly constant at 5". That is the dwell time needed for the pressure to drop and the action to cycle with enough force to do the job reliably. 16" carbines came about because makers were selling M4geries with carbine handguards hand over fist, not because it was the right thing to do. After all, the customer always thinks he's right. Carbine gas on a 16" is too early in the cycle, which is why they have harsher recoil compared to the others.

Anyone can cut a barrel to whatever they want, the right way to make a DI gun function is to use the correct dwell point for the gas block regardless of where the handguards fit or if a FSB is mounted in front. Nobody wants a problem child.

It's significant that dissipators were prototypes, not issue or production in any numbers. Apparently they were successful in proving rifle gas on 16" has problems - and it was better not to do it quite like that.

I building a 16" with rifle handguards, midlength, with an aluminum railed front block to anchor the guards and mount a front BUIS. I agree, the NM free float would be nice IF it was available in something besides steel. Since it's just a threaded tube with a handguard cap, it's possible to just fabricate one in aluminum, and I'm still researching the possibility.