How to measure barrel to determine gas tube length

[Petrock]

I have an AR style barrel that I don't remember what the gas system length should be.

From the barrel extension to the muzzle is 20.5 inches.

The gas port is:

From barrel extension: 13.5 (344mm)
From front of barrel extension: 12.25 (313mm)

I would think due to the length that it's a rifle length system.

Please advise

 

[Blastattack]

That’s definitely rifle length.

 

[Petrock]

That’s definitely rifle length.

How is the measurement done?

I need to learn the process.

 

[Canadian Psycho]

There is only 3 different gas tube lengths. The is rifle length (12") Mid length (10") and Carbine length (7"). All lengths are roughly there. The rifle length with have a 12" hand guard, mid length a 9" hand guard and the carbine a 7"

 

[Petrock]

There is only 3 different gas tube lengths. The is rifle length (12") Mid length (10") and Carbine length (7"). All lengths are roughly there. The rifle length with have a 12" hand guard, mid length a 9" hand guard and the carbine a 7"

Does this mean that every gas tube will be the same length in each class regardless of manufacturer?

 

[redshooter]

Does this mean that every gas tube will be the same length in each class regardless of manufacturer?

Yes, there's also pistol length and you can get longer than Rifle for Barrels over 20", but they're not common (more common in Pistol lengths).

 

[diegocn]

Does this mean that every gas tube will be the same length in each class regardless of manufacturer?

In general yes.

This chart comes from TNA website:

The way I look at it: the gas tube needs to stick past the barrel extension (end of your barrel) for about 1". On the other end, it needs to stick past the gas port on your barrel for about 0.6" (because the gas tap hole is drilled 0.6" from the end).

So if end of your barrel extension to gas port is ~13.5", add 1.6" to that, you'll get ~15.1", which means you need a rifle length gas tube.

 

[Petrock]

Diegocn,

That is exactly what I was looking for but couldn't find through google.

Thank you

 

[adamg]

There is only 3 different gas tube lengths. The is rifle length (12") Mid length (10") and Carbine length (7"). All lengths are roughly there. The rifle length with have a 12" hand guard, mid length a 9" hand guard and the carbine a 7"

You missed intermediate length, and pistol length.

 

[Ex3dy]

You missed intermediate length, and pistol length.

also short pistol, rifle +1,+2,+3 and armalite rifle and mid

 

[DANS40X]

ArmaLite AR-10 B series (M14mags) & AR-10A series (Pmags) gas tubes are approximately 1/2" longer than AR-15 gas tubes.

ArmaLite only manufactured rifle & carbine length systems,no intermediate length.

ArmaLite gas journals are either .750"-3/4" or .875"-7/8" diameter.

SASS is there adj piston system.

 

[Daver_II]

There is only 3 different gas tube lengths. The is rifle length (12") Mid length (10") and Carbine length (7"). All lengths are roughly there. The rifle length with have a 12" hand guard, mid length a 9" hand guard and the carbine a 7"

Nope.

There are also extended rifle +2
AND some proprietary ones from companies like proof research.

Also. Nothing procludes having a carbine or midlenght on a long barrel.


TNA has a good graphic on their site that shows you how to measure.

 

[Dietz]

Does this mean that every gas tube will be the same length in each class regardless of manufacturer?

Except KAC and a few others, yes.

Like the above poster said, there are proprietary gas tubes, LMT's MRP system has a straight gas tube.

 

[Ex3dy]

ArmaLite AR-10 B series (M14mags) & AR-10A series (Pmags) gas tubes are approximately 1/2" longer than AR-15 gas tubes.

ArmaLite only manufactured rifle & carbine length systems,no intermediate length.

ArmaLite gas journals are either .750"-3/4" or .875"-7/8" diameter.

SASS is there adj piston system.

TNA lists 12.53" for AR10 Armalite mid length gas tube, 11.75" for AR15 mid length. Intermediate AR15 is 13.25". not sure which Armalite rifle uses mid length but 14" barrel would be my guess. No intermediate length is correct.