COMPARING INTERNAL VS EXTERNAL PISTON DRIVE SYSTEMS

[ArmaLite]

Comparing internal and external piston drive systems: http://tiny.cc/zs1re

[imschur]

Thanks Armalite!

[Waveman]

Interesting -- thanks!

[survivalshop]

Well , I read that twice & still don't see how you can call Stoner's design an internal piston .

If you look up in a dictionary, it will tell you a "piston " is connected to a rod of some sort & in a cylinder. The way the system of "Direct impingement " works is a pocket in the BC is filled with gas until it reaches a certain pressure enough to unlock the bolt & force the assembly back .

I do see a piston in the external design , as in , a piston, surrounded by a cylinder , attached to a rod of some sort & exerting the force of the gas at the piston rear ward to disengage the BCG.

I see no piston surrounded by a cylinder,connected to any kind of rod in the DI system . It IS a collection of gas in a pocket .

Now I know I should not be speaking up dispelling or disagreeing a fact or facts by a Major manufacturer of firearms , but mechanically ,I don't see it .

[imschur]

Does the BCG become the piston itself?

[98Z5V]

The bolt is the "piston" in a DI gun - complete with it's gas rings (piston rings).  The BCG is the cylinder that the "piston" rides in.  No joke.  ;D

It's just a piston without a connecting rod.  <thumbsup>

[survivalshop]

The gas rings on the BOLT are just a seal for gas's building up in the chamber.

The bolt doesn't move until the bolt carrier is forced back far enough until the cam pin is moved out of its locking position to release (turn ) the bolt from the locking lugs.

I see the bolt carrier as more of a valve than a piston . Just because it moves & gas pressure is put to it , does not necessarily make it a piston.

You can argue it both ways & you can agree one way or the other ,but one fact that can not be disputed , Mr. Stoner came up with a revolutionary system to work the action of a firearm & really can not be compared to any thing before it . 

[98Z5V]

The gas rings on the BOLT are just a seal for gas's building up in the chamber.

Those gas rings are present on a piston gun, too, brother - right on the piston.  <thumbsup>

[survivalshop]

Those gas rings are present on a piston gun, too, brother - right on the piston.  <thumbsup>

Yes some gas piston designs have replaceable " rings " for sealing , but they all reciprocate. The bolt doesn't move until its UNLOCKED by the rear ward movement of the BC .

That bolt being locked in place until gas pressure is built up in side the BC to move it ,makes it an unlikely candidate as a piston .

[mrmackc]

It seems that everyone has their own opinion as to how the AR direct gas impingment system works. Some of the postings are spot on, others not quite exactly correct. impingement is the key word.  I have researched gas operating systems on firearms  since I worked in a USMC reserve units Infantry companies armory back in 1963.

 

The Marine's handbook was my first reference material, and I have continued to study firearms gas operating systems. I have also found good information on the internet. Here is a link to one of the more detailed explanations:  http://ar15barrels.com/prod/operation.shtml

[Sisco]

If you own an Armalite, or for that matter, any AR type, The Armalite Technical bulletins on their website make for great reading.