AR Gas Systems

[rucker]

I was wondering how the barrel gas system relates to the buttstock buffer tubes. Are they completely separate things or do they need to match somehow?

For example if a barrel says it uses a "Rifle Length Gas System" and the buttstock says it mounts on "Carbine tubes" does that mean they don't work together? Would you have to have a barrel that uses a carbine gas system?

[hammAR]

Here is how they relate, others can chime in about "matching".......................

The mechanism of operation for the rifle is known as direct gas impingement. Gas is tapped from the barrel as the bullet moves past a gas port located under the rifle's front sight base. The gas rushes into the port and down a gas tube located above the barrel. The gas tube runs from the front sight base into the AR-15's upper receiver. Here, the gas tube telescopes into a “gas key” which accepts the gas and funnels it into the bolt carrier. The movement of gas into the bolt carrier forces the bolt and carrier backwards in a line with the stock of the rifle. As the bolt carrier moves towards the butt of the gun, the bolt begins to turn and unlock from the barrel extension. Once the bolt is fully unlocked it begins rearward movement along with the bolt carrier. The cam pin is responsible for the bolt's rotation as it follows a groove cut into the carrier that twists and forces the bolt to unlock. Once the bolt is unlocked, the bolt carrier and bolt continue to move towards the butt of the gun and the chambered casing is extracted and ejected out the side of the upper receiver.

A return spring located behind a buffer then pushes the bolt carrier back towards the chamber. A groove machined into the upper receiver traps the cam pin and prevents it and the bolt from rotating into a closed position. The bolt's locking lugs then push a fresh round out of the magazine, up the feed ramps and into the chamber. As the bolt's locking lugs move past the barrel extension, the cam pin is allowed to twist into a pocket milled into the upper receiver. This twisting action follows the groove cut into the carrier and forces the bolt to twist and “lock” into the barrel’s extension.

[David]

When I put a telescoping stock on one of my fixed-stock ARs a few years ago, the new buffer tube was identical in length to the old one (Colt fixed stock, Busmaster collapsible stock). The stock was shorter, but the tube didn't go all the way to the end on the old one anyway. You can get heavier buffers, but if I'm not mistaken it's just to change the rate of fire, rather than because different barrel lengths might require different buffers. I haven't done too much of this, though, so I can't say it is supposed to work that way.

[rucker]

Thanks guys. I also found this which is pretty cool: http://www.barnesengineering.com/AR15an ... /index.htm

[JFettig]

That animation isn't quite right. The gas key isn't correct, It angles back more and hits the rear cavity so it can actually push against something, if it went where it is it wouldn't do anything, you'd have a single shot.

Jon

[someone1980]

How often do you replace buffer springs?

[rucker]

That animation isn't quite right. The gas key isn't correct, It angles back more and hits the rear cavity so it can actually push against something, if it went where it is it wouldn't do anything, you'd have a single shot.

Jon

Well I got the idea anyways

So, does anybody know if there is a difference between using a carbine tube or a rifle tube? Is the difference just the physical length or is there something else to it?

[mnglocker]

So, does anybody know if there is a difference between using a carbine tube or a rifle tube? Is the difference just the physical length or is there something else to it?

It's the length as far as I know, and that will play into the buffer spring you then use.

[rucker]

So, does anybody know if there is a difference between using a carbine tube or a rifle tube? Is the difference just the physical length or is there something else to it?

It's the length as far as I know, and that will play into the buffer spring you then use.

Right. So it doesn't affect your barrel choice or anything other than that particular assembly?

[JFettig]

You should be ok with either one on whatever barrel.

The buffers are different lengths to make up for the different length tubes, I'm not sure if the springs are different though, they could be. The buffers also have different weights, just use the right spring with the right buffer and you should be ok.

I personally prefer an A1 or A2 stock over a collapsible. They are so floppy, I really don't like them.


Jon

[Spartan117]

How often do you replace buffer springs?

Close to, if not never.

[Spartan117]

I personally prefer an A1 or A2 stock over a collapsible. They are so floppy, I really don't like them.

Standard CAR or M4 collapsible stocks are floppy, but there are other options:

Magpul M93B, CTR, UBR, LMT Sopmod, Vltor, etc.

My favorite:



ETA: Don't forget mid-length gas systems! Smoother than carbines, but more compact than rifle.

[Pat]

I personally prefer an A1 or A2 stock over a collapsible. They are so floppy, I really don't like them.

Standard CAR or M4 collapsible stocks are floppy, but there are other options:

Magpul M93B, CTR, UBR, LMT Sopmod, Vltor, etc.

My favorite:



ETA: Don't forget mid-length gas systems! Smoother than carbines, but more compact than rifle.

Spartan: Which stock is the one you have shown in the pic?

[Spartan117]

I personally prefer an A1 or A2 stock over a collapsible. They are so floppy, I really don't like them.

Standard CAR or M4 collapsible stocks are floppy, but there are other options:

Magpul M93B, CTR, UBR, LMT Sopmod, Vltor, etc.

My favorite:



ETA: Don't forget mid-length gas systems! Smoother than carbines, but more compact than rifle.

Spartan: Which stock is the one you have shown in the pic?

That's a Magpul M93B. In my opinion, it's the best AR stock available. It's tight enough that feels like a fixed stock. I've got four of them! (In three different colors )

[Pat]

Very nice. I like the grips, too!

However we should all remember that EBR's are supposed to be black, or they're just not evil enough...