What is gastube and why do some upgrade it?

[aespinoza101]

Hello everybody
Noob here...and need answers on AR-15 gas tube. Spent considerable time searching the forum and web but could not find an answer.

What is the purpose of a gas tube? Do all AR's have them? And finally, why do some choose to upgrade/change it out?


Thanks in advance for your input.

aespinoza101

[CleverName]

The gas tube lets some of the expanding, hot gas go from the barrel near the muzzle and move the bolt carrier.

Not all AR15s have them, piston uppers will not.

Fatboy gas tubes were used to slow down carbine builds, in order to save some wear and tear on the system.

Some people think direct impingement is a bad idea, that it dirties the upper and heats the bolt carrier unnecessarily and has an adverse effect on reliability. Others think these problems are overstated.

[aespinoza101]

So if I want a high reliability rifle I should look away from direct impingement system? What are my other options. I currently have a Stag-15 on order and have not decided on upper yet.

Thanks,

[Linus]

Here are some basics on the gas operated reloading.

http://en.wikipedia.org/wiki/Gas-operated_reloading

The AR uses a Direct Impingement system that is described in detail below.

http://en.wikipedia.org/wiki/Direct_impingement

[Boots]

well.... besides the added cost of a gas piston setup, you will have an easier time of cleaning your AR.
I myself am in the process of ordering a gas piston upper for my first "from scratch" build.
Other benefits from less fouling, and this is what I've heard from others, is that a gas piston rig can lead to more reliability in the field.. and the reason why AK's are so reliable in dirty situations.

As for me.. my main motivation is cleaning... I hate cleaning! (but always do because I detest even more shooting from a dirty firearm.)

[aespinoza101]

Clevername and Linus, thanks for your help. I also found this site with good animation of both systems.

http://www.armytimes.com/projects/flash/2007_02_20_carbine/

[Linus]

So if I want a high reliability rifle I should look away from direct impingement system? What are my other options. I currently have a Stag-15 on order and have not decided on upper yet.

Thanks,

No just keep you AR clean and lubricated and it will be as reliable as a piston upper without burning a hole in you wallet.
But if you do want a piston upper contact ADDAX he'll take car of ya.
Here's a link:

http://www.adxtactical.com/store/pc/viewPrd.asp?idcategory=137&idproduct=1011

[aespinoza101]

The upper assembly on adxtactical is looking really nice. I might consider that. thanks.

[CleverName]

You might want to check out Pat Rogers' thread on ARFCOM, "What parts break in a carbine course?". Basically, as long as you run your rifle wet, and you aren't burning through thousands of rounds on FA per day, you should be OK with a DI gun.

[aplinker]

There are a few gas tubes out there that are "upgrades." They're designed to overcome the overpressure and/or the cyclic rate of the short carbine system. Both of these are better fixed by just changing to a mid-length (longer) gas system.

A lot of the so-called "issues" with ARs are due to the carbine length gas system.

A lot of the reliability of the AK is due to the sloping shape of the round and its wide tolerances, along with the piston system.

Gas pistons have their benefits, but also drawbacks. If you're looking for a shorter rifle (say, 14.5" or less) their benefits can overcome their drawbacks.

The PWS system Addax uses is very nice.

I would suggest not sweating the details of DI vs. Piston. My best suggestion to you is to buy a well-built mid-length gassed DI rifle and just keep it lubed and wipe down the BCG after range sessions.

well.... besides the added cost of a gas piston setup, you will have an easier time of cleaning your AR.
I myself am in the process of ordering a gas piston upper for my first "from scratch" build.
Other benefits from less fouling, and this is what I've heard from others, is that a gas piston rig can lead to more reliability in the field.. and the reason why AK's are so reliable in dirty situations.

As for me.. my main motivation is cleaning... I hate cleaning! (but always do because I detest even more shooting from a dirty firearm.)

[gemini1]

So is a piston upper more expensive than the standard uppers on DI system?
Is the piston uppers being sold as widely as the standard ones?

If this method is such a benefit on reliability and of course less time cleaning the rifle, how come I don't seem to hear a lot about it?

[CleverName]

DI guns are more accurate, less expensive, and a LOT more common.

[rayra]

No just keep you AR clean and lubricated and it will be as reliable as a piston upper without burning a hole in you wallet.
But if you do want a piston upper contact ADDAX he'll take car of ya.
Here's a link:
http://www.adxtactical.com/store/pc/...idproduct=1011

This.

[glockwise2000]

I disagree with clevername. A gas psiton system doesn't diminish it's accuracy compared to the traditional DI system. I know it could be like a couple of hundred bucks extra but you can't replace the issue that it is so much easier to clean. I got my GP from Addax Tactical and I could give those guys a big credit. Not only that the product was excellent, they would even teach you to how to dismantle and clean your new GP system FTF. Ralph and Chris are great guys over at Addax. Plus the GP system is guaranteed for life and the upper it self has a 5 year guarantee. They are just down in Chatsworth in San Fernando Valley.
Cleaning is a big mess specially when you would shoot often like me. I used to have 2 DIs before (I still have them, but I don't shoot on them anymore). My buddies and I tried a gruelling and expensive 2000 round test on the Addax GPU and not a shot failed.

[J_Rock]

I disagree with clevername. A gas psiton system doesn't diminish it's accuracy compared to the traditional DI system. I know it could be like a couple of hundred bucks extra but you can't replace the issue that it is so much easier to clean. I got my GP from Addax Tactical and I could give those guys a big credit. Not only that the product was excellent, they would even teach you to how to dismantle and clean your new GP system FTF. Ralph and Chris are great guys over at Addax. Plus the GP system is guaranteed for life and the upper it self has a 5 year guarantee. They are just down in Chatsworth in San Fernando Valley.
Cleaning is a big mess specially when you would shoot often like me. I used to have 2 DIs before (I still have them, but I don't shoot on them anymore). My buddies and I tried a gruelling and expensive 2000 round test on the Addax GPU and not a shot failed.

Like it or not an over head gas piston is negatively affecting accuracy. It is possible you arent shooting under conditions to see this but the piston imparts a down and rearward force on the barrel which usually results in vertical stringing. Heavier barrels can alleviate this but in general a GP upper will not be as accurate as a DI upper. Even Chris can attest to this which is why dont see GPs on precision ARs.

GPs have their uses but in the OPs case he will be better served with a DI upper,for the OP a $12 gas tube will do the same thing as a $400 piston. With an extra $388 you can upgrade your barrel or your trigger.