another gas tube question

[sagebrush]

bought a ballistic advantage barrel #babl308003m. it's a .308 16" tactical government, mid length barrel, modern series. gas port measures .070 takes a .750 gas block. measured the gas tube length as 11.125, this matches no length on any charts i could find. did go back to ballistic advantage and they list a gas tube for this barrel, but couldn't find the length listed. wondering if the port should be drilled to .085 or .090. maybe with the shorter tube .070 will work?

[sagebrush]

was to late to edit. did find that the gas tube listed for barrel, shows length as 11.75. it is a normal length

[jim3326]

You'll need to open up the port to .090 and the tube is probably short at 11.125". The tube needs to end up in the middle of the key cutout in the upper receiver.

[98Z5V]

21 hours ago, sagebrush said:

was to late to edit. did find that the gas tube listed for barrel, shows length as 11.75. it is a normal length

That's a regular midlength AR15 gas tube size.  You need to see where it ends in the cam pin cutout in the upper receiver.  It should end right in the middle of the cam pin cutout.  Take a pic and post it up here in this thread.

18" midlength gas with a 0.750" journal needs a gas port diameter damn close to 0.085"  - if you have a proper recoil system.  16" midlength, with 2" less dwell time, will need to be 0.090" port, maybe a touch more - with a proper recoil system.

So, now that I've said that twice - what recoil system are you running on this gun?

[98Z5V]

21 hours ago, sagebrush said:

measured the gas tube length as 11.125,

So...   you measured 11.125"...

21 hours ago, sagebrush said:

was to late to edit. did find that the gas tube listed for barrel, shows length as 11.75. it is a normal length

...and they say it should be 11.750"

[sagebrush]

1 hour ago, 98Z5V said:

So...   you measured 11.125"...

...and they say it should be 11.750"

as i found even later in my research here i found your instructions on how to measure for gas tube length. i failed to add the half inch. so my measurement should have been 11.625. i would assume the 11.750 won't bottom out. haven't ordered yet was measuring so i would be sure to get right tube.(that didn't work so well). as for the recoil system, i am going to order the armalite ar10 carbine buffer and tube kit. the number is ar10rekit01

[98Z5V]

Gas tubes extend 0.600" past the gas tube roll pin.  If you can measure the end that's in the gun, all the way to the gas tube roll pin, add 0.600" and that's the overall length you have.  It's not a half inch.  It's 6/10th inch.  Big difference, when you're looking for proper gas timing.  

Gas tubes are too easy to just remove, and measure end to end.  That's what I'd recommend.  Just pull it, and check it.