Piston / Gas PLUG /OpRod Questions

[kospap]

hi all!

I have been studying the various AR15 piston conversions and I have stumbled to a long hanging question of mine on what is a piston, a gas-key, and an op-rop....

or better phrased when a gas action transfering part is called a Piston / Gas Key /OpRod?

<span style="font-weight: bold">Op-Rod.....</span>self explanatory for me...a rod that transfers piston momentum to the bolt carrier....
But is it the same when it gets the hot gasses itself, like an AK?
Does it makes any difference if it is permanently attached on the BCG or not?

<span style="font-weight: bold">Piston...</span>to me it is the intermediate between gasses and the Op-Rod

<span style="font-weight: bold">Gas-Key....</span>this is where I am lost.....I know there are parts in the M1 & M14 rifles that are called that, and I am sure the same goes for the MAG....
but what exactly is a Gas-Key?

Is there a real difference between a Gas-Key and a piston, or is it semantics only?

And to mix things up more
There are AR gas piston conversion that have 3 parts in line that move (LWRC and BlackRifle systems)....Any reason to sort nomenclature on these cases?

TNX a bunch..kostas

more trouble....
http://en.wikipedia.org/wiki/Z-M_Weapons_LR_300
<div class="ubbcode-block"><div class="ubbcode-header">Quote:</div><div class="ubbcode-body">The gas key is extended beyond its normal length to form an operation rod</div></div>

 

[Sebben]

Re: Piston / Gas Key /OpRod Questions

oops got gas key confused with gas plug OPs post was a little confusing. Don't mind me read below...

 

[Captain Moroni]

Re: Piston / Gas Key /OpRod Questions

The gas key is the part that sits on top of your BCG on a DI gun piston guns either replace the gas key or the whole BCG.

 

[SSSamurai]

Re: Piston / Gas Key /OpRod Questions

The gas key in a direct impingement system receives the gas from the gas tube, so if you wanted to stretch the definitions you could look at it as a sort of piston. I've heard people refer to the whole BCG as a piston, but I don't think looking at it that way is accurate, and may just create more confusion. In a DI system there is no need for an op-rod or piston, since the gas pressure acts directly on the BCG. The other parts are needed when using a piston near the gas port, which receives the gas and pushes back on the op-rod, which pushes back on the carrier key to move the BCG.

 

[acidone]

Re: Piston / Gas Key /OpRod Questions

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: SSSamurai</div><div class="ubbcode-body">The gas key in a direct impingement system receives the gas from the gas tube, so if you wanted to stretch the definitions you could look at it as a sort of piston. I've heard people refer to the whole BCG as a piston, but I don't think looking at it that way is accurate, and may just create more confusion. In a DI system there is no need for an op-rod or piston, since the gas pressure acts directly on the BCG. The other parts are needed when using a piston near the gas port, which receives the gas and pushes back on the op-rod, which pushes back on the carrier key to move the BCG. </div></div>

If any part of the bolt carrier group is a "piston" i'd have to say it is the bolt itself. I think its kind of hard not to call something a piston if it has piston rings installed on it. I know we all call them gas rings, but they pretty much do the exact same thing as a piston ring installed on a piston.

 

[SSSamurai]

Re: Piston / Gas Key /OpRod Questions

I was just trying to get away from calling anything in a DI gun a piston, but you're right about the bolt. And I think the same logic could be applied to calling the whole BCG a piston.
Also, the OP asked about the op-rod being attached to the BCG, like the way an AK works. What you're describing is a long-stroke piston, where the piston and op-rod travel the entire length of the cycle with the bolt group. This is different from a short-stroke system, in which the piston pushes the op-rod back a fraction of the distance, imparting force to the bolt group, but not traveling with it as it cycles. The stress on the carrier key in this system is why many of them are now machined as one-piece carriers, instead of being bolted on like gas keys in a DI system.

 

[kospap]

Re: Piston / Gas Key /OpRod Questions

ooops.....I got to apologize for not using the proper word in a critical question...

I was meaning to say <span style="font-weight: bold">gas plug </span>as .sebben correctly noted....(obvious be the reference in the M14/M1)

So when a part is a gas plug and not a piston?

note..I corrected the title

 

[SSSamurai]

Re: Piston / Gas Key /OpRod Questions

The gas plug is usually a thread on cap for the gas system, which is removable to access the piston and op-rod. The gas plug is sized according to the amount of gas needed to correctly operate the system, so it is important to have the right size for the system and ammo used in it. There are also adjustable gas plugs available.

 

[Sebben]

Re: Piston / Gas Key /OpRod Questions

I'll be damned... had it right accidentally on purpose the first time!