AR15.Com Archives
 16 inch barrels with rifle length gas system
EternalVigilance  [Member]
10/8/2007 7:08:12 AM EST
I was hoping you guys could school me on this. 16 inch barrels with rifle length gas systems are referred to as "middys" correct?

What are the ins and outs of this? I am trying to decide between getting an regular LMT 16 inch upper or a 16 inch upper with a rifle length gas system. What are the pro's and cons?


Are there any reliability issues, or any negatives at all, about using a rifle length gas system in a 16 inch barrel? It seems like the barrel being shorter would affect the pressure of the gas and how effectively the gas system works. Is there any real reason they didn't design carbines like this in the first place?

The biggest attraction to me is the increased sight radius. I love to shoot irons.

I also ordered an RRA 6-position collapsible stock. Can I use the same buffer spring and just get a rifle buffer to put in the collapsible stock if I go with a "middy" upper?



Is CMMG the best option for a "middy" upper?
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Stickman  [Industry Partner]
10/8/2007 7:12:35 AM EST

Originally Posted By EternalVigilance:
I was hoping you guys could school me on this. 16 inch barrels with rifle length gas systems are referred to as "middys" correct?

What are the ins and outs of this? I am trying to decide between getting an regular LMT 16 inch upper or a 16 inch upper with a rifle length gas system. What are the pro's and cons?


Are there any reliability issues, or any negatives at all, about using a rifle length gas system in a 16 inch barrel? It seems like the barrel being shorter would affect the pressure of the gas and how effectively the gas system works. Is there any real reason they didn't design carbines like this in the first place?

The biggest attraction to me is the increased sight radius. I love to shoot irons.

I also ordered an RRA 6-position collapsible stock. Can I use the same buffer spring and just get a rifle buffer to put in the collapsible stock if I go with a "middy" upper?



Is CMMG the best option for a "middy" upper?




Midlength systems have a gas system that is mid way between a carbine and a rifle. Midlength carbines tend to run nicer as the gas pulse is smoothed out, which results in reliability and a slightly more gentle felt recoil. You are correct in there is a different amount of pressure with the difference in port position.

CMMG is a good dealer, and can certainly help you out.

Stickman  [Industry Partner]
10/8/2007 7:17:56 AM EST

Originally Posted By EternalVigilance:
The biggest attraction to me is the increased sight radius. I love to shoot irons.




If you like the increased length on the sight radius, another thing to think about is running a longer rail, and pushing out your front sight even farther.


Here is a picture of a standard midlength.




Here is a picture of another 16" barreled weapon, but with the sight out farther.

DemonLoneWolf  [Member]
10/8/2007 7:22:08 AM EST
If you want a cheap set up with a long sight radius but compact, then just get a mid-length gas system (hidden by handguards) with a rifle length sight radius. CMMG offers one, but they also offer a rifle length gas system with 16" barrel, which is generally not reccomended. They have everything though.
TaylorWSO  [Life Member]
10/8/2007 7:39:10 AM EST
You want a dissapator, not a longer gas system. Just install a low profile gas block unr the handguards with a "Fake" FSB pinned on, or a Rifle length FF tube on a 16" barrel
DemonLoneWolf  [Member]
10/8/2007 7:41:07 AM EST

Originally Posted By TaylorWSO:
You want a dissapator, not a longer gas system. Just install a low profile gas block unr the handguards with a "Fake" FSB pinned on, or a Rifle length FF tube on a 16" barrel


Yes exactly.
EternalVigilance  [Member]
10/8/2007 8:14:47 AM EST

Originally Posted By DemonLoneWolf:

Originally Posted By TaylorWSO:
You want a dissapator, not a longer gas system. Just install a low profile gas block unr the handguards with a "Fake" FSB pinned on, or a Rifle length FF tube on a 16" barrel


Yes exactly.




Does anybody make one that you can purchase that already has these features? I think bushmaster does but i want extended feedramps and I also don't want to have to get a taller front sight post.


The midlengths mentioned in the first few replies have 18 inch barrels correct? I want a 16 inch barrel.
KC-ROUGHNECK  [Member]
10/8/2007 8:26:14 AM EST

Originally Posted By Stickman:

Originally Posted By EternalVigilance:
The biggest attraction to me is the increased sight radius. I love to shoot irons.




If you like the increased length on the sight radius, another thing to think about is running a longer rail, and pushing out your front sight even farther.


Here is a picture of a standard midlength.
stickman.rainierarms.com/galleries/AR15%20Carbines%20II/IMG_6652%201028%20WEVO%20Stick.jpg



Here is a picture of another 16" barreled weapon, but with the sight out farther.
stickman.rainierarms.com/galleries/Magpul/IMG_2667%20Stick.jpg



Hey stick, what is the length of the handguards in the bottom pic.

edlmann  [Member]
10/8/2007 8:32:00 AM EST

Originally Posted By EternalVigilance:
16 inch barrels with rifle length gas systems are referred to as "middys" correct?


No. It means a longer handguard (by about 1.5", I think), a fsb moved forward accordingly, and a correspondingly longer gas tube. Allows the bayonet lug to be functional with a 16" barrel, among other things.
Saginaw79  [Member]
10/8/2007 8:55:39 AM EST
I shot a dissipator with full length gas and a 16" barrel. It was the nicest shooting 'carbine' I have ever shot. I was very impressed by the softer recoil impulse than a regular carbine
TaylorWSO  [Life Member]
10/8/2007 3:31:46 PM EST

Originally Posted By Saginaw79:
I shot a dissipator with full length gas and a 16" barrel. It was the nicest shooting 'carbine' I have ever shot. I was very impressed by the softer recoil impulse than a regular carbine


If you shot a dissy, it didnt have a rifle length gas system on a 16 barrel. It has a ML/CAR gas on a 16 barrel with rifle handguards.

If you put a Rifle gas system on a 16" barrel it wouldn't run.
jh308  [Team Member]
10/8/2007 4:19:36 PM EST

Originally Posted By TaylorWSO:
If you put a Rifle gas system on a 16" barrel it wouldn't run.


Wouldn't it be fine as long as you opened up the gas hole appropriately? I understand that it might not be quite as reliable w/weaker ammo or in cold weather. Sorry to hi-jack, but I'm curious as to why it would be a bad choice all around as I'm thinking of purchasing this for my next build:
CMMG's 16" M10R w/Full Gas
sic_ness  [Member]
10/8/2007 4:50:52 PM EST
There seems to be alot of confusion in this thread as to what constitutes a middy and dissipator and the like.

*ahem*

A run of the mill carbine with a carbine length gas system has a gas system around 7" long.

A mid length rifle has a 9" gas tube, and results in smoother recoil with less pressure on the operating system.

A 'dissipator' can be two things. All have a full length handguard and sight radius of a rifle.
Some (like the original bushmaster pattern dissipator) have a low-profile gas block in the carbine position underneath the rifle-length handguards.
Others have a full length rifle gas tube in the normal rifle position. Alot of the time the gas port needs opened up (to .10" or so, iirc) to function reliably.

comprende?
Farns223  [Member]
10/8/2007 5:21:21 PM EST

Originally Posted By jh308:

Originally Posted By TaylorWSO:
If you put a Rifle gas system on a 16" barrel it wouldn't run.


Wouldn't it be fine as long as you opened up the gas hole appropriately? I understand that it might not be quite as reliable w/weaker ammo or in cold weather. Sorry to hi-jack, but I'm curious as to why it would be a bad choice all around as I'm thinking of purchasing this for my next build:
CMMG's 16" M10R w/Full Gas


That's what I have!!!!

jh308  [Team Member]
10/8/2007 6:03:00 PM EST

Originally Posted By Farns223:


That's what I have!!!!

img.photobucket.com/albums/v65/Farnsrocket/gun%20stuff/IMG_9495.jpg


Very nice! How are you liking it so far?
Stickman  [Industry Partner]
10/8/2007 6:32:01 PM EST

Originally Posted By KC-ROUGHNECK:


Hey stick, what is the length of the handguards in the bottom pic.




Both are 16" barrels.
Farns223  [Member]
10/9/2007 2:36:44 AM EST

Originally Posted By jh308:

Originally Posted By Farns223:


That's what I have!!!!

img.photobucket.com/albums/v65/Farnsrocket/gun%20stuff/IMG_9495.jpg


Very nice! How are you liking it so far?


To be honest, I just got it together last week and haven't had a chance to shoot it!!
Hopefully CMMG made a barrel config that works...I would think so or they would be doing some work on it!
nhsport  [Team Member]
10/9/2007 3:57:59 AM EST

Originally Posted By DemonLoneWolf:

Originally Posted By TaylorWSO:
You want a dissapator, not a longer gas system. Just install a low profile gas block unr the handguards with a "Fake" FSB pinned on, or a Rifle length FF tube on a 16" barrel


Yes exactly.


This is one of those things where I know that a dissy would work very well for me (I am at the age and eye condition where sight radius is VERY important) and the design should run better all things considered but DAMMIT it just doesn't look right! Generally I am all about function but sometimes form just plays into the deal!
Farns223  [Member]
10/9/2007 5:34:00 AM EST

Originally Posted By nhsport: it just doesn't look right! Generally I am all about function but sometimes form just plays into the deal!


I think it is an aqcuired taste. Personally, I fell in love with the look right away.....something about the short barrel stickin out and the full handguard.....gives it an almost shorter than 16" look.....I dunno, kind of an HK91 look.
jh308  [Team Member]
10/11/2007 6:57:18 PM EST

Originally Posted By 97ss10:
Not trying to hijack or anything but I looked on the CMMG site and didn't see where I could get the mid length gas tubes. I found the gas blocks but no tubes. Maybe I'm just blind but where would you find those if not there?

Not sure where they are on CMMG's site, but here's some other places that I've had really good dealings with:
bravo co
Denny's Guns
Del-Ton
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