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

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15 hours ago, Albroswift said:

Spikes Tactical 14.5" 5.56 1:7  5/8" journal midlength gas .078 port diameter

^^^  That's interesting, right there, brother.  :thumbup:  They went skinny on that journal size, down to a .625", and they upped the port diameter to compensate.  That combo with a standard .750" journal would be a 0.070" gas port.  They thought about that one.   :hail:

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18" AP AR10, .308, .1098 and waiting for 3mm drill bits to enlarge port to .1110.  Rifle buffer, rifle buffer spring. All AP. FailZero BCG. Factory port was .078 and it wouldn't run. Ammo was 150gn match bullets,LC brass. 42.5-43gn 4166 or 4895.

Actually it ran ok for a few 100rds. Which took a while to achieve. Very accurate rifle. After a couple cleanings it wouldn't run. It wasn't ejecting then feeding a round on top of the spent brass causing lots of crunched wasted brass. I thought it was over gassed. Bought an adjustable block and that led me to conclude it was under gassed. Bored a .1098 hole and problem solved. Since Im running the gas block closed off at .1098 I want to farther increase the port to 3mm which I believe is between 17/64" and 1/8".1110.  giving me room to adjust the block as necessary.

My 16" AP also M5, 308 is running .078 port, .072 fact? carbine buffer and spring. The 16" has the S2? Smooth hand guard and she is lights out and wlll run 110 3200fps load up to Nosler 180green tips no problems. Just my experience. Both are fantastic, reliable auto-feeders with BDX optics and paired with a Kilo 2200 range finder. 

Edited by ApD2
Validate factory gas port dimensions

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10 minutes ago, ApD2 said:

18" AP AR10, .308, .1098 and waiting for 3mm drill bits to enlarge port to .1110. 

Interesting.  You never stated the gas system for that 18" barrel.   Maybe start a new thread here on your build, instead of cluttering this thread with specific-bun build info. 

Start a new thread, and I'd like to talk about this gas port diameter that you have.  :thumbup:

Here's the Build Section link:

https://forum.308ar.com/forum/114-member-builds/

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If it ran and then quit running...you aren’t undergassed. I’d bet something came loose with the gas tube or something is somehow plugged up. Dismantle and check it out. Saw a gas tube roll pin issue cause something similar once on a buddies gun at the range. Tube came free. 

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7 minutes ago, DNP said:

If it ran and then quit running...you aren’t undergassed.

 

I was gonna state that - when he starts his own thread on this all, and doesn't continue it in the "Gas Port Information Thread"...

Not the "Gas Port Guessing Thread..."

No harm on you, brother - just on him.  Wrong place to decide to launch your gas port questions - in an information thread...

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Looking at this thread I remembered that I never notified y'all about my Faxon 16" pencil bbl. .750" journal, 3/32" drill barely fits, making the port 0.09375".

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9 hours ago, mtrmn said:

Looking at this thread I remembered that I never notified y'all about my Faxon 16" pencil bbl. .750" journal, 3/32" drill barely fits, making the port 0.09375".

What caliber...

What gas system...

Give the full details on the barrel - something more than a 16" Faxon pencil with a .750 journal, and a 0.93" port diameter.  We're missing alot of information here, on this barrel.

Edited by 98Z5V

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PSA build.

16" Faxon pencil, .308, 1/10, "mid length" requiring 12 -1/16" gas tube. Kaw Valley 5.6 oz buffer with Sprinco orange spring. 0.093" gas port in a .750" journal.

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