AR gas hole location in regards to rifling

AR/M4 AR Technical Discussion
1

Is there any kind of military spec for AR gas hole location in regards to rifling? I see people talking a about gas hole size and location on a frequent basis around here but no one seems to mention if it is drilled in a rifling groove.

https://www.m4carbine.net/archive/index.php/t-87315.html

FWIW I’ve read on AK forums that it is important. There is a guy out there that was cutting barrel stubs in half with a wire EDM machine and the gas hole was consistently in the groove on ’74 barrels both krink length and the normal 16” length.

2

Satern made me some barrels with the gas hole in the groove - so if it is important to you, you can have them make your barrel. But no, the military does not ask for it.

3

Krieger has been putting gas ports in the groove for years…

4

My gas hole is in the groove. My wife’s gas hole is in the groove. I think everybody I know, their gas hole is in the groove. I haven’t asked specifically but that’s my best guess.

Sorry, couldn’t resist.

5

Interesting the Russians do it but we don’t. Maybe the bullet sheer thing is not the reason. Russian bullets ate steel jacketed while ours are copper. Maybe it’s port errosion. AK probably have a longer military life exspectancy.

6

You can also use a special tool to chamfer the inside of the hole. I had that done to the 300 BLK AK.

7

Yeah, this is rather surprising and hard to believe for me. With all the emphasis placed on the location in the AK, why doesn’t the military think it matters for the AR? :confused:

8

Interesting the Russians do it but we don’t. Maybe the bullet sheer thing is not the reason. Russian bullets ate steel jacketed while ours are copper. Maybe it’s port errosion. AK probably have a longer military life exspectancy.

I think the life of the AK and its realibility is one of the internet fabled things like the super awesome Mk 262 rounds and anything with “zombie” in front of it.

I had more jam clearing practice when shooting AKs than any other gun by a long shot.

9

And which gun is more accurate? :cool:

10

Not specifying the location of the gas port to the rifling makes a rifle more accurate?

11

apparently.

12

Mk 262 is good ammo, if you do your part. But, alas there is no wonder bullet.

As for the AK. It all depends on who made yours. Most all domestically produced AK’s cannot be compared to the real deal AK’s for a variety of reasons. Number one being the mods to the FCG.

13

Wouldn’t it be a pain in the butt to align the gas hole in the barrel of the AR? The barrel extension is threaded on. This sets the timing of the rifling at the gas hole location. I guess you would need to have many barrel extensions to get one that is perfect, and even then you would probably be sacrificing perfect headspacing for having your hole in the groove.

14

Of course not. It’s just absurd that the AK would be gas port position sensitive considering it’s a marginally accurate weapon anyway.

And the lack of port location placement certainly hasn’t hurt the accuracy of the USGI rifle.

15

No more so than in a match M14 barrel.

16

Then why bring it up?

The AK-74 was redesigned specifically because gas port location and shape caused accuracy to fall below Soviet requirements.

We know this. This thread was asking if there is a specification for it, and if not, what makes the AR different.

17

Why would one need to chamfer the inside of the port?

18

dull bits and incorrect feeds/speeds will raise a burr on the edge of the hole. It’s an area that is hard to access with convention deburring methods. Otherwise, removing material that will erode away eventually seems, strange.

Currently, wracking my brain to come up with a test to determine if gas port location affects accuracy.

19

I didn’t bring it up. I had no idea that the AK’s port was position specific until I read it here. :rolleyes:

20

Read an interesting article once discussing location of gas port versus land/groove, lots of tests and pics, just can’t remember where I saw it :(. Anyway, conclusion was, it didn’t seem to matter, aside from the holes that were 1/2 in the land and 1/2 in the groove seemed to exhibit less erosion after extended use. :confused: