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survivalshop

Barrel Gas Port Size,308/338/260/243 etc.

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  I'm starting a thread on this in hopes the STAFF here will make it Pinned . Only info needed here is if you know your Barrels Port size , post it here , with Manufacturer , Gas system length  & Barrel length & if you had to make any changes to it to make it work if you had issues.

 

  Kreiger Criterion  308 ,16" HB  , Rifle Gas system  ------   0.1095 "

  Sharps , 25-45 Sharps , 20" LT , Rifle gas system ----       0.09375"

Here is some info from Tactical Machining

 

AR-15 GAS PORT SIZES

Disclaimer: These are lists of compiled information from multiple sources. While we make our best effort to test and produce these should be considered for reference only. Any time you start messing with the gas port on your rifle you run the risk of destroying the barrel or causing it to be over gassed. It is much better to slowly work your way up to what you would be happy with.

AR-15 Platform 5.56mm
20" rifle 5.56   0.0935
20" rifle 5.56   0.096
20" rifle 5.56   0.098
16" mid 5.56   0.078
16" mid 5.56   0.081
16" car 5.56   0.0625
16" car 5.56   0.065
16" car 5.56   0.07
14.5" car 5.56   0.067
14.5" car 5.56   0.086
11.5" car 5.56   0.081
11.5" car 5.56   0.089
24" rifle 5.56   0.089
AR-15 Platform 7.62x39mm Conversion
20" rifle 7.62x39   0.12
20" rifle 7.62x39   0.125
16" car 7.62x39   0.078
16" car 7.62x39   0.081
16" car 7.62x39   0.0938
DPMS LR-308 Style Rifle
18" rifle 0.308   0.0960
18" car 0.308   0.0635
16" mid 0.308   0.078
16" mid 0.308   0.081
16" car 0.308   0.07
16" car 0.308   0.073
16" car 0.308   0.076
20" rifle 0.308   0.0935
20" rifle 0.308   0.096
AR-15 Platform 300 BLK Conversion Subsonic Ammo
16" car 300 BLK UNSUPRESSED 0.12
16" car 300 BLK UNSUPRESSED 0.125
16"  car 300 BLK SUPRESSED 0.106
16"  car 300 BLK SUPRESSED 0.11
16" pistol 300 BLK UNSUPRESSED 0.067
16" pistol 300 BLK SUPPRESSED 0.086
9.5" pistol 300 BLK UNSUPRESSED 0.093
9.5" pistol 300 BLK SUPPRESSED 0.093
8.1" pistol 300 BLK UNSUPRESSED 0.104
8.1" pistol 300 BLK UNSUPRESSED 0.12
8.1" pistol 300 BLK SUPRESSED 0.086
8.1" pistol 300 BLK SUPRESSED 0.093
         
         
AR-15 Platform 300 BLK Conversion Supersonic Ammo
16" pistol 300 BLK UNSUPRESSED 0.0625
16" pistol 300 BLK SUPPRESSED 0.059
16" car 300 BLK UNSUPRESSED 0.099
16" car 300 BLK SUPPRESSED 0.093
9.5" pistol 300 BLK UNSUPRESSED 0.073
9.5" pistol 300 BLK SUPPRESSED 0.067
8.1" pistol 300 BLK UNSUPRESSED 0.076
8.1"  pistol 300 BLK SUPPRESSED

0.067

The 300 Blackout data has been compiled from Micro MOA

Edited by survivalshop

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5.56 info here-

Ballistic Advantage .223 Wylde SPR barrel: 18" .223 Wylde SPR Stainless Steel Rifle Length AR 15 Barrel w/ Ops 12, Premium Series, 1:8" twist

Gas port diameter: 0.095"

 

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Another 6.5 Grendel barrel spec:

Faxon Firearms 6.5 Grendel gas port info: Match Series- 18" Gunner, 6.5 Grendel, MIDLENGTH GAS SYSTEM, 416-R, 5R, Nitride, Nickel Teflon Extension - Gas Port diameter = 0.077".

Edited by 98Z5V

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PSA 18" Stainless .308 barrel, "midlength" gas system.  0.073" fits, 0.076" does not fit.

This gas port is too small.

Edited by 98Z5V

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Found the thread with our original gas port data:

 

Found it by looking for this chart, that I knew I'd seen here.  .308 min and max gas port sizes, by barrel length, from one specific reputable manufacturer:

GAS PORT DIAMETER AND LOCATION.jpg

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Rainier Arms Select .308 barrel, stainless, 18", true AR15 midlength gas system.  Gas port diameter 0.081".

Edited by 98Z5V

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.308 win 16 inch rifle gas(AR15rifle), X-Caliber barrel ended up at .1005", runs everything there.

Edit; .750" diameter at the gas block.

Edited by jtallen83

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.260 Remington info:

Wilson Combat .260 Remington Tactical Hunter barrel, 20"  rifle gas,1:8" twist.  Recessed 11-degree target crown.  416R stainless.  Gas port diameter is 0.071".  Weight is 1205 grams/42.5 oz/2.65lbs.

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Wilson Combat .338 Federal  

Gas Port Size  .0705" by my chinese calipers on my chinese drill bits.............
 Gas Block Seat     .750" Diameter 
 Gas System     Intermediate-Length (13.25") the tube delivered with the barrel was actually 13 3/16" by my Stanley tape.
 Length     14.7"
 Rifling     1:10, RH, Six Groove, Precision Button Rifling
 

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22 hours ago, jtallen83 said:

 Intermediate-Length (13.25") the tube delivered with the barrel was actually 13 3/16" by my Stanley tape.

Very interesting, brother...   :thumbup:

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Ballistic Advantage Modern Series, Mk12 profile, 5.56 chamber, 1:7" twist.

18" 5.56 SPR Rifle Length AR 15 Barrel w/ Ops 12, Modern Series

This one:  https://www.ballisticadvantage.com/18-inch-556-spr-rifle-cmv-modern-barrel-ops12.html

Gas port diameter is 0.095", 18" 5.56 barrel, rifle gas. 

This is very close to what an 18" rifle gas .308 Win barrel needs to be. Here's the barrel referenced:

18in_5.56_spr_modern_1.jpg

 

 

 

 

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12.5" SIG 716 .308Win piston-system barrels - that we run as DI Gas Guns... These are were the CDNN blow-out barrels for $49.95.

Mine was a 12.5" barrel with a  0.750" journal diameter, 0.070" gas port diameter.  Dwell time measurement on my barrel was 3.500", center of gas port to end of barrel crown - this might be important later, because you carefully need to measure YOURS.  On that barrel config, I needed a gas tube that was exactly 11.000" long. Perfect calculation and measurement, once the custom gas tube arrived from White Oak Armament. Gas tube was perfect, and WOA nailed what I asked them to do/make.

P1080702.JPG

Functional test - this 0.070" gas port diameter gonna work on a 12.5" barrel, with a 3.500" dwell time?...  :popcorn:    First round lock back, virgin gun, lubed properly, one round in the mag. Gas port was right on it.  This gun runs.

Recoil system details are:  7.000" internal depth AR15 receiver extension (what comes with the SBA3 kit), hybrid (home-cobbled) 2.500" buffer that's 5.7oz, and a Sprinco Orange spring.

There are some people reporting, and posting accurate verified pics, of needing a gas tube length that was 11.250".  That's a longer gas tube, and that shortens dwell time, on an already shortass barrel.  No details on their recoil systems, but that's something to be aware of - if you HAVE one of these barrels, you better measure three times before you order a custom gas tube.  And the only place on the planet that is making custom AR gas tubes is White Oak Armament.  If you're building one of these, pay attention...  :thumbup:

Edited by 98Z5V

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8 hours ago, 98Z5V said:

And the only place on the planet that is making custom AR gas tubes is White Oak Armament

And Al's shop when he can't wait for the nationals to finish and WOA to get back to work!

Mine came out perfect at 11-3/16" If I remember right. Had to open the port up a bit, think I ended up with .079 and backed down just a bit w/ AGB.

Ditto on Orange spring and 5.6 buffer. Also ran fine with the longer extension/ buffer and a Tubbs spring w/ AGB a little closer to W/O.  

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6mm ARC.  Ballistic Advantage Mk12 SPR profile barrel, 18" rifle gas.  Gas port diameter is 0.097". 

https://forum.308ar.com/uploads/monthly_2020_06/P1080710.JPG.6c12c9bcd97f91f6b297f7f0bd8dce2f.JPG

 

 

 

 

 

 

 

P1080712.JPG.90b7441a0edf3e7db52eceffc636430b.JPG

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10 hours ago, jtallen83 said:

BSF 6.5 Grendel 18 inch with rifle gas, .875 journal diameter, .093 gas port diameter.

 

That's gonna work, brother.   :thumbup:

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