Carbine or Mid-length Gas for 16" barrel?

Blastattack

Blastattack

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Well, as the title states, should you opt for a Carbine or "Mid-length" gas system on a 16" AR-15 barrel? Are there any other considerations that need to be... considered for either choice, such as bolt carrier type or parts availability?
 
In theory, a mid-length gas system provides lower operating pressure providing smoother operation and less wear. There's a longer sight radius for iron sights if you use them. Personally, I like the look of a mid-length system, too. IIRC, other than the gas tube, barrel and handguards, all other parts are the same.

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They both work. The mid length has been out long enough that almost everyone and their dog is producing them so I wouldn't grant much credence to the availability of parts argument. That argument would have been valid about half a decade ago. Get either one with a low profile gas block and a floating tube/rail.
 
one thing about a carbine length system is that with its high pressure and shorter piping, it will self clean a bit better. I know my carbine length AR REALLY tosses the empties. 6-8 feet when it was stock. Lots of room if there is some plugging up of the port, tube etc. If its really soft shooting and has just enough energy left to eject the spent brass, and something small goes wrong, its gonna stop up.
 
JR Hartman said:
one thing about a carbine length system is that with its high pressure and shorter piping, it will self clean a bit better. I know my carbine length AR REALLY tosses the empties. 6-8 feet when it was stock. Lots of room if there is some plugging up of the port, tube etc. If its really soft shooting and has just enough energy left to eject the spent brass, and something small goes wrong, its gonna stop up.
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The carbine is more violent because the extraction cycle begins earlier and the spent casing has not returned to its final size in the chamber before the pressure has completely subsided. This means more force is needed to pull the casing out. it is HARDLY an ideal thing. The quick fix by the US Navy that came out about 13 years ago was to increase the tension of the extractor spring by adding an o-ring. That becomes a standard practice now by many manufacturers to make sure their bolts work in carbines.

If it sucks , why it is done this way? This goes back to the 10" XM177, and then the need to mount bayonets on carbines.

The mid length is a much better system. It is softer shooting. It has lower port pressure, longer dwell time, later extraction initiation, lower bolt velocity, less bolt bounce probably and less critical to anything that affects the timing of the system that leads to malfunction, like enlarged gas port from erosion.
 
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mebiuspower said:
Vltor A5 system resolves the issue of carbine length gas tube.
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VLTOR's FOG, or "Forward Offset Gas" system also helps solve the issue of pressure and dwell time with short barrels. The gas tube goes nearly all the way to the muzzle, and uses a purpose-built flash hider/expansion chamber to give proper dwell time and lower port pressures.

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Carbine length gas on anything from 14.5 and up is an abomination. Midlength rifles cycle smoother, and are less abusive on the components of the gun.
 
Colt has been doing carbine length gas systems in their 16 inch rifles for quite a long time, I seriously doubt thats an "abomination" as someone else has put it, i don't think anyone here on this forum knows better than colt.
 
mikethebike said:
Colt has been doing carbine length gas systems in their 16 inch rifles for quite a long time, I seriously doubt thats an "abomination" as someone else has put it, i don't think anyone here on this forum knows better than colt.
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Good for colt. All I'm saying is if you have the option, taking carbine length over midlength when you have the option to run the latter is a fail. Carbine length rifles produce more heat, pressure, and fouling while causing the bolt to travel faster; this comes with its own set of side effects. A midlength rifle will produce a lower recoil pulse than a carbine length rifle.
 
Cool, thanks guys. I'm looking at building an AR with a custom dissipator style barrel. Good to know that mid length is the best choice. Also I am a machinist, so such a creation is not beyond my abilities.
 
abomination eh? yea, tell that to Colt, Bushmaster etc.

from what I have read here, I have learned that the mid length is better in some ways and if I build my own or buy an other upper, I will go with mid length. However, just because something works better doesn't automatically make the other system an abomination.
 
JR Hartman said:
abomination eh? yea, tell that to Colt, Bushmaster etc.

from what I have read here, I have learned that the mid length is better in some ways and if I build my own or buy an other upper, I will go with mid length. However, just because something works better doesn't automatically make the other system an abomination.
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Abomination is perhaps a bit aggressive. By default if mid is superior to carbine then calling carbine an abomination is inline even if its a bit harsh.

Tdc
 
Non-phixion said:
Good for colt. All I'm saying is if you have the option, taking carbine length over midlength when you have the option to run the latter is a fail. Carbine length rifles produce more heat, pressure, and fouling while causing the bolt to travel faster; this comes with its own set of side effects. A midlength rifle will produce a lower recoil pulse than a carbine length rifle.
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Yeah it is good for Colt. The Carbine length gas system was designed to work. Shortest barrel possible, work everytime, for the soldier in the field. Mid lengths are the "abomination"
Yes, they do work, and the impulse is softer, it may run cooler and it may be easier on parts. BUT; with all the different ammo, buffers, gas port sizes etc in use with civvie mid lengths, there is no guarantee it will cycle ammo without a hiccup. Especially for someone buying an AR15 for the first time.

A good carbine gas system is usually overgassed. (larger port size)
Depending on your ammo (223, 5.56) you can 'tune" your carbine to make it shoot softer. Buffers, springs, muzzle device.....

I own both types of uppers. If you are not shooting suppressed full auto, a good Colt , DD, BCM, LMT type carbine gas system will last just as long as any mid length gas system weapon.
 
Non-phixion said:
Good for colt. All I'm saying is if you have the option, taking carbine length over midlength when you have the option to run the latter is a fail. Carbine length rifles produce more heat, pressure, and fouling while causing the bolt to travel faster; this comes with its own set of side effects. A midlength rifle will produce a lower recoil pulse than a carbine length rifle.
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And BTW, an overgassed midlength is just as violent on parts as a carbine.
 
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