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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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  • 1 month later...

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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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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  • 2 months later...

KAK Industry 5.56 barrel.  12.5" Midlength gas (this is rare for a 12.5" - most are Carbine Gas).  0.935" gas port (#42 drill bit).  The dwell time on this combination is 2.875" with a 0.750" gas block journal.

We'll see how this works out. I think the diameter is a little small, for the dwell time, but it'll put my math to the test, if it does/doesn't shoot. If it does - that's weird for my gas port math.  We'll see.  It might need to go up, from what I know...

VALUE-LINE 5.56 NATO 12.5 INCH MID MELONITE BARREL

https://forum.308ar.com/uploads/monthly_2021_07/IMG_0473.JPG.d505d9ad2845d1c33fc8629d31dc32e0.JPG

Edited by 98Z5V
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  • 5 weeks later...

Well, ^^^  that little fucker shocked me, and ran like a CHAMP right out of the gate!  From first round, single-round lock back, to beating it up.  I passed if off to Matt and DirtBike Tommy, they yanked trig on it hard - and it just ran.  And ran, and ran.  This is a solid barrel from KAK - it WORKS, just like it is.  They did it well.  :hail:

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  • 3 months later...
1 hour ago, tjbLR10 said:

LR 10 .308 22" barrel, rifle length .091 port.

Port changed to .091 from .085 cycle issues are now alleviated running strong, good accuracy. 

 

Who made the barrel?   What's the brand?   That will help greatly down the road if somebody else here asks about it.   :thumbup:

Edited by 98Z5V
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  • 2 weeks later...

The last .260 Rem barrel I received from Wilson Combat was the 20" rifle-gas barrel with the 0.750" gas block journal size, and That needs to be 0.080".  The one I received was 0.076", and that was a TIGHT fit.  They're doing better, making baby steps up from the 0.070" that my first one was at.  But, they still haven't learned.  This thing needs to have an 0.080" gas port diameter, for this barrel config. 

I'll fix it.

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  • 1 month later...

Update on this Wilson Combat .260 Rem barrel - I fitted it to an Aero M5 upper at the gun shop today, and checked gas port location with a regular AR15 rifle-length gas tube...

It's short.  As Fuk.  Barely gets into the front of the cam pin cutout.  It still needs the Armalite AR-10 Rifle gas tube to be right.  I'll get that coming, or go visit/call Armalite, and get it on the way.  I knew that was going to be the case, just knew it.

Wilson Combat hasn't learned the "gas port LOCATION" rule yet...  They make badass, super-accurate barrels.  They just need to do the rest of it, and make them perfect already...

Edited by 98Z5V
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  • 2 months later...
6 hours ago, 308FAN said:

Wilson Combat 20" .308 .875 gas Journal, Rifle Length 15.5" tube, Super Sniper, Fluted. 

.075" port

It short strokes, I believe the port is too small. Still researching before I drill it.

1st post ever

 

 

4 hours ago, Armed Eye Doc said:

Welcome to the forum.  @98Z5V can calculate what size the hole needs to be.

Needs a 0.090" gas port diameter - or very, very damn close to that.

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11 hours ago, Armed Eye Doc said:

Welcome to the forum.  @98Z5V can calculate what size the hole needs to be.

I ran into the same problem with my WC build (18" Barrel), Polished Boron BCG, Gas, and biller set (all Wilson Combat). Had to use the forward assist to push the BCQ against the bullet. Armalite A5 spring & buffer spring and an A5 Smoke Composites tube. 

Edited by cafemike
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