Why don't all military and to a lesser extent civillian semi auto rifles.............

[cslinger]

Come with an an adjustable gas port. Now I have shot just about everything under the sun and have a pretty decent working knowledge of firearms but I am by no means a gunsmith or engineer so this question might be one of those hey stupid that was a stupid question.

Anyway it seems to me like an adjustable gas port is a wonderful idea that would allow the broadest range of ammunition choices and extend your military's choice of small arm's life cycle.

Why is this not more common? Is it because the average grunt is going to set it to the maximum setting for maximum functional reliability but also batter their weapon to death by doing this?

Why no adjustable settings on rifles such as AR series, M1A series, AK series and to a lesser extent certain civillian hunting autos like say a Browning BAR?

It just seems like this added functionality would make for a much wider availability of ammunition choices for both military and civillian shooters alike.

 

[Nightcrawler]

Well...the AK doesn't need one.

See, the AK's gas system is way overpowered. That's one of the reasons it's so reliable. It's akin to having a FAL with the gas cranked down so as to slam the bolt back with the most force. Tuning the gas on the FAL allows you to reduce battering on the rifle, by using only enough power to reliably cycle the rifle.

I've heard that the M14's gas system is "self-regulating", but I don't know what this means. Perhaps it has a vent to release excess gas, or something.

 

[dbshabo]

I agree, I think it would be a good improvement on many rifles. I would guess the $$ factor is why we don't see it on more rifles.

Shabo

 

[DMK]

Probably for one less thing for a soldier to mess with. Keep It Simple. It did seem to work OK for the FAL though.

It seems that most military guns are designed for a standard spec ammo. Then all ammo issued (eg. NATO 7.62x51) is made to that spec. A good example of that is the twist rate in the M16. When they changed the ammo, they had to change the twist rate.

Theoretically, you could set the gas adjuster on your FAL to a certain setting and leave it there, providing you only shot surplus NATO 7.26x51 and cleaned it properly. Some NATO ammo is a little bit hotter or weaker than others, but not to a huge extent.

 

[bernie]

I had asked myself this very question earlier this week driving down the road and reached the same conclusions of DMK and dbshabo.

 

[98m]

Surprise , Surprise. Although the adjustable gas system would seem to be superior in my own testing it proved the oposite.

The self-regulating or self-adjusting system of the M14 works with everything from low power cast bullet loads to high power military ammo.

My experience with the adjustable gas systems has not been good. It is a real pain in the behind to get them adjusted just right and then as the gun becomes dirty you must stop to readjust them again. This type of system will get you killed in combat.

I personally will take the self-adjusting system of the M14 anyday, I have never had a problem with it but I cannot say the same of other systems that required manuel adjustment.

 

[Joe Demko]

Fulton Armory offers an adjustable gas tube for the AR-15, but I've never met anybody who actually has one.

 

[wanderinwalker]

DMK,

I dunno if this really matters, but the twist rate of the AR-15/M-16 series was setup to handle the 55gr ball first. When 62gr ball came out, we needed more spin. Now that we're using 77gr and 80gr bullets in competition ARs, everybody is glad for the "over-stabilized" twist rates!

With the M-1 Garand, one must use powders in the 4895 burn-rate range to prevent gas system damage. I've tried reloaded 168gr BTHPs and even some old LC match (174gr IIRC) and while no physical harm came to the rifle, it definitely shoots better with 155gr Palma-type bullets.

As to the adjustable gas system, one more complexity to screw up or break. No thanks, the fixed systems work fine.

Take care,
~Nate

 

[DMK]

I dunno if this really matters, but the twist rate of the AR-15/M-16 series was setup to handle the 55gr ball first. When 62gr ball came out, we needed more spin.

Wasn't that what I said?

 

[wanderinwalker]

DMK,

Yeah, you're right... (Apolgizes here)

But mil-spec is subject to change, or so we both agree. Yet it seems that the change here didn't affect the gas-port, just the barrel twist. From experience I have learned that the AR-type direct-gas impingement is fine without adjusting gas-port pressure, within reason. It's a mature, refined design. The M-14 likewise seems to have few problems. The M-1 Garand will happily beat itself apart with the wrong ammunition. It'll run, for certain, just not at its optimum.

Again, adjustable gas system good in theory, but mostly unneccessary in practice.

 

[El Tejon]

Another moving part to break. Puteth no laser, no phaser, no wind speed indicator upon one's weapon.

 

[ReadyontheRight]

I have an old "dial a duck" Remington Sportsman 58 shotgun with the adjustable gas system and it seems to jam more often than the modern self-adjusting systems. May be more of an operator error though.