Gas Port Size

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sscav
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Gas Port Size

Post by sscav »

What is the correct gas port size for a 16 inch, carbine barrel?
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bangbangping
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Re: Gas Port Size

Post by bangbangping »

Subs, supers, both? Suppressed or not? All of the above?
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dellet
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Re: Gas Port Size

Post by dellet »

Much debated subject as there never was an actual “spec” published by AAC.

What I can tell you is that probably 90% of all barrels out there, have a much bigger port than will ever be needed. A properly set up rifle, in normal conditions, with what would considered a normal weight bullet of 200 grains+, will work fine with .100” port. That includes all factory sub sonic ammo I have tried and hand loads as light as 168 grains without a suppressor. That does not include every factory load now available.

Wilson combat used to list port size in the barrel schematic section of all their barrels. 16” carbine gas was .109”. That is probably a good number for all ammo, all conditions, without a suppressor.
300 Blackout, not just for sub-sonics.
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Flatliner
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Re: Gas Port Size

Post by Flatliner »

My latest build (10.5" pistol gas) started at .076. That was a touch too small to reliably manage a variety of unsupressed subs for what its worth.
sscav
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Re: Gas Port Size

Post by sscav »

Right now I'm shooting supers.

The load is Reformed LC cases, 18.0 gr H110. 125 gr SMK
sub-oldguy
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Re: Gas Port Size

Post by sub-oldguy »

If one was to enlarge the gas port in the barrel, what would be the proper procedure if one was not to take it to a gunsmith?

I assume that it would be a matter of a larger drill bit but I'm wondering what effect it has on the rifling and any burrs that may result.

Or just take it to a proper professional?
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bangbangping
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Re: Gas Port Size

Post by bangbangping »

sub-oldguy wrote:If one was to enlarge the gas port in the barrel, what would be the proper procedure if one was not to take it to a gunsmith?

I assume that it would be a matter of a larger drill bit but I'm wondering what effect it has on the rifling and any burrs that may result.

Or just take it to a proper professional?
When I've done it I used a numbered bit set and enlarged the hole a few thousandths at a time. Any burr will be very thin and can be knocked off with a brass brush. Put a 1/4" wooden dowel in the bore to stop the bit from pinging the opposite side of the bore when it goes through.
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dellet
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Re: Gas Port Size

Post by dellet »

I’m curious about current size, how large you want to go and why.
For shooting supers, .085” is more than enough.
300 Blackout, not just for sub-sonics.
bamashooter
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Re: Gas Port Size

Post by bamashooter »

Is there a spreadsheet / database here / elsewhere that we can populate showing 300blk barrel brand name, gas port size, etc? Similar to this for .223 / 5.56:

https://docs.google.com/spreadsheets/d/ ... =766121382

Here's the "input" page for the above: https://docs.google.com/forms/d/e/1FAIp ... g/viewform

Thanks
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John A.
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Re: Gas Port Size

Post by John A. »

sub-oldguy wrote:If one was to enlarge the gas port in the barrel, what would be the proper procedure if one was not to take it to a gunsmith?

I assume that it would be a matter of a larger drill bit but I'm wondering what effect it has on the rifling and any burrs that may result.

Or just take it to a proper professional?

The proper procedure is to drill it to the next smaller size, then finish with a reamer in the diameter you are wanting.

With a reamer, there is virtually no chance of having a burr, so.....that's why I stick to reamers.
When those totally ignorant of firearms make laws, you end up with totally ignorant firearm laws.
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