GAS PORT DIMENSIONS

[barrelwrench]

Is there thread that addresses gas port size by manufacturer, carbine and rifle length barrels.

[C4IGrant]

Is there thread that addresses gas port size by manufacturer, carbine and rifle length barrels.

No. There really is only two set standards (that very few follow). The 14.5" M4 and the 20" A2/A4.

All middy's, 10.5/11.5/12.5/18" all have a GP size that the manufacturer believes works the best. Some have a good GP size, but most are WAAAAY over gassed.

Typically all your none mil-spec guns are going to be over gassed (BM/RRA/Oly/DPMS/Stag/SW/etc).



C4

[rsilvers]

If you took one of these over-gassed rifles and shot them on a FA lower with weakish ammo - say commercial .223 ammo - what cyclic rate in FA would you get?

And if that is not known, what cyclic rate would you set them at, with typical commercial .223 ammo, if you were picking the gas port?

[C4IGrant]

If you took one of these over-gassed rifles and shot them on a FA lower with weakish ammo - say commercial .223 ammo - what cyclic rate in FA would you get?

And if that is not known, what cyclic rate would you set them at, with typical commercial .223 ammo, if you were picking the gas port?

It would be faster for sure. How many more RPM? Hard to say. Most likely 100 more.


C4

[rsilvers]

I mean what do you think such an over gassed upper, as you have run across, would run in FA -

600, 650, 700, 750, 800, 850, 900, 950, 1000, 1050 RPM?

Cause that is a good way to know if something is over-gassed. I am not sure how else to tell besides high speed video.

[C4IGrant]

I mean what do you think such an over gassed upper, as you have run across, would run in FA -

600, 650, 700, 750, 800, 850, 900, 950, 1000, 1050 RPM?

Cause that is a good way to know if something is over-gassed. I am not sure how else to tell besides high speed video.

Don't really know as there are too many variables to correctly estimate the RPM.

For those of us that shoot guns with correct and or small gas port's, we can go by feel. Another good idea is to simply measure the GP size.


C4

[orionz06]

Don't really know as there are too many variables to correctly estimate the RPM.

For those of us that shoot guns with correct and or small gas port's, we can go by feel. Another good idea is to simply measure the GP size.


C4

Is there a better choice for say an 11.5" barrel that will not have a suppressor right away but will eventually? DD, BCM, or other?

[C4IGrant]

Is there a better choice for say an 11.5" barrel that will not have a suppressor right away but will eventually? DD, BCM, or other?

Yes. The optimal choice would be a Switch block from Noveske (if you wanted a gun for suppressed use and one without.

Both BCM and DD typically use GP's on the smaller size. So those are also a good option I think.

For me, SBR's are so obnoxious that I ONLY shoot them suppressed. So having a gun setup for suppressed 365, is the best option (YMMV).



C4

[AR15barrels]

Typically all your none mil-spec guns are going to be over gassed (BM/RRA/Oly/DPMS/Stag/SW/etc).

Having personally measured about a hundred colt and bushmaster gas port diameters, I can state that they are the same within 14.5" and 16" carbine gassed barrels.
All the others, it's anyone's guess.

[AR15barrels]

For those of us that shoot guns with correct and or small gas port's, we can go by feel.

+1.

I have developed gas port diameters for about every possible configuration by test firing.
I have reached a point where I now just know what a gas port diameter needs to be when considering all the factors.

[Iraqgunz]

Why does it seem that BM barrel gas ports open faster than Colt ones? Is it a material issue?


Having personally measured about a hundred colt and bushmaster gas port diameters, I can state that they are the same within 14.5" and 16" carbine gassed barrels.
All the others, it's anyone's guess.

[AR15barrels]

Why does it seem that BM barrel gas ports open faster than Colt ones? Is it a material issue?

Most likely the difference between the 4140 they use and the 4150ish steel that Colt uses.