Gas port size for a 14.5" Colt socom barrel?

[pezboy]

Thought about cutting to 10.5" to avoid that but wasn't sure if gas port size would need to be changed for dedicated suppressor use. I've read that .062" is perfect for 11.5" but not sure on 10.5".

You can get up to ~11.4" ATF measured from an M4 barrel without it looking goofy. Colt 11.5" barrels are 11.625" ATF measured FWIW.

No matter what length you go with, I would suggest keeping the .062"-.063" gas port and see if it works. If it doesn't, slowly open it until it does.

[tom12.7]

For the OP's dedicated suppressed usage, the factory .0625" port may work very well. Just depends on the attributes of the selected ammunition, can, etc..

[Iraqgunz]

I'm keeping that number unless I see more. That said, there is still the .001 tolerance rule.

Looks like I need to update my notes. I got them from some bearded fella in Az. You might know him. :-)

[Iraqgunz]

I would be very careful about having any barrels cut, and any specific Port sizes unless you know for a fact they are correct.

[pezboy]

I'm keeping that number unless I see more. That said, there is still the .001 tolerance rule.

The spec for the port on an M4 barrel is .0620-.0630". I have no reason to doubt the M4A1 SOCOM barrel is any different.

[MistWolf]

According to my copy of Black Rifle II, in the chapter about the M4/M4A1 Carbine, page 69

...Further testing was conducted with the gas port diameter of 0.0625". Colt sent six XM4 carbines in this configuration to Fort Dix for hot weather (150 degree F) and cold weather (-50 degree F) testing, where it was determined that this gas port diameter performed well in cold temperatures, with no carbines failing due to "lack of power"

[Wayne Dobbs]

I would be very careful about having any barrels cut, and any specific Port sizes unless you know for a fact they are correct.

There's a post that's bursting with wisdom. Unfortunately, many folks don't recognize, appreciate or use wisdom.

And the 14.5" and 16" barrels from Colt do come with a .062 gas port per specs.

[M Sadler]

I might argue that there's nothing scientific about the port sizes Colt used in the production of the M16 rifle or M4 carbine. Each gas port is finished with the decimal equivalent reamer of an ANSI size drill.

Rifle = 3/32, 0.0938
Carbine = 1/16, 0.0625

I doubt a thousandth of inch made enough of a difference in tuning to warrant the cost of purchasing custom reamers to finish gas ports.

[MistWolf]

Colt first submitted the XM4 (the M4 prototype) for testing with a .062" gas port and had reliability trouble with one of the types of ammo. They opened up the gas port to .0625 and "it was determined that this gas port diameter performed well in cold temperatures with no carbines failing due to 'lack of power.'"

So in testing, they found a small change made a noticeable difference

[jpmuscle]

Colt first submitted the XM4 (the M4 prototype) for testing with a .062" gas port and had reliability trouble with one of the types of ammo. They opened up the gas port to .0625 and "it was determined that this gas port diameter performed well in cold temperatures with no carbines failing due to 'lack of power.'"

So in testing, they found a small change made a noticeable difference

How is gas pressure inside the system and what percentage of a difference does .005 make? Im genuinely curious.