ashokgodara,great info xl
just curios to know.what you are plannig to install a long stroke piston or short stoke one.it will be too early but i can ask also to buljit paji whats his plan on long stroke or short stoke.kindly shed some lights on advantage ot disadvantage of both systems thanks
Neither. The mil-spec M4 carbine does not use a gas piston.
What I will be building is a lightweight M4 look alike (an M4gery, if you like ) with a 16" barrel. Baljit will probably be building his a little differently
I will be using the standard "Direct Impingement"(DI) system with a carbine length gas tube.
Generally an AR-15 with 16" barrels will use the "Carbine Length" gas system
AR-15's with 18" barrels will use a "Mid Length" gas system
and AR-15's with 20" barrels will use a "Rifle Length" gas tube.
Here is how Direct Impingement works:
image from HERE
The image recycles about every four or five seconds.
When the cartridge is fired, the gasses pushing the bullet up the bore will vent up through a "gas port" in the bore. This gas is forced down a "gas tube", back towards the receiver.
When this gas impacts (or impinges on) the "gas key" that is affixed to the top of the bolt, it pushes the bolt carrier group back (against spring pressure) to extract and eject the fired cartridge and load a fresh on into the chamber.
image from HERE
The gas key is that silver thing that is attached to the top of the bolt. The receiver end of the gas tube sits inside of it.
I hope this helped your understanding of the system. Please do not hesitate to ask questions if something is not clear.