View Full Version : difference between mid length gas & dissipator ?

12-14-2008, 9:06 AM
What's the difference between a mid length, dissipator, and M4 gas block
locations on a 16" barrel ?

I've searched high & low and my understanding so far is that the mid
length gas block is closer to the muzzle on a 16" barrel than a M4 gas
block. But is a dissipator gas block further back from the muzzle than a
mid length ?

Just how much difference is there, in inches, between the locations of
all these gas block configurations ?

And does it really matter ?

12-14-2008, 9:26 AM
M4 and original bushmaster brand dissipators are carbine length which is about 7 inches if I remember right. Midlength is 9 or so inches.

12-14-2008, 12:04 PM
the m4 uses a carbine length gas system.

so does the dissipator.

the midlength uses a midlength gas system.

the sight on the m4 is at where the gas system is

the sight on the dissipator is at the end of the barrel

the sight on the midlength is where the gas system is.


here's pictures of what the gas system lengths are. the shorties use carbine length, the ones slightly longer are mid length and the longest ones are rifle length. i think there's also extended (longer than rifle) and intermediate (between rifle and middy) but someone else can clarify that.

if you are looking for a recommendation, i'd say get nothing less than a mid length gas system and go with the longest sight radius you can afford.

is there a such thing as a middy dissipator?

i have a middy with a rifle length rail that has a flip down buis...

12-14-2008, 12:05 PM
Wow I never knew that either, I thought the dissipator was a full length gas system, never saw a picture of one until now, there is a gasblock AND a FSB. ....