Hit the Gas Piston

The big piston AR debate might be long dead, but different piston systems are still very popular. This is especially true when it comes to modern firearm design. Guns like the MCX and MPX use gas piston systems. These systems are in no way new and have been around for a very long time. Guns like the M1 Garand and AK 47 use gas-piston designs. Today we are going to explore the systems, and their advantages. 

Gas and Semi Autos 

When we say gas piston we are of course referring to the gas created by burning gunpowder as the round travels down the barrel. With any gas-operated gun, including short and long-stroke piston, direct impingement, etc a bit of gas is bled off to operate the weapon. This gas travels through a gas block attached to the barrel. What happens next determines the ‘type’ of system. 

What’s a Short Stroke Gas Piston System? 

The short-stroke gas piston design is one of the more popular modern systems. Rifles like the SCAR, the aforementioned MCX, the CZ Bren, and many more use a short-stroke design. This design is not new and was also used in the AR-18, and the VZ 58.

When the gas meets a short-stroke gas piston assembly it is driven rearwards and the assembly strikes the bolt carrier. This sends the bolt carrier rearwards and allows the weapon to cycle. A spring around the assembly often drives the piston back into place in the gas block. 

Credit SIG Sauer

As the name implies, short-stroke systems move only a short bit when struck with gas. This type of piston does not travel the full length of the operating group when the weapon fires. The piston is separate from the bolt carrier often a multipart piece that’s a bit more complicated than a long-stroke system. It ‘shoves’ the bolt carrier and then resets.

The benefits of this system include an overall lighter weapon, as well as reduced recoil. Less mass moves rearward and therefore you feel less recoil. Downsides are few, with early systems carrier tilt was a concern, and some guns tended to be ammo picky based on pressure. These days the kinks are largely gone and short gas piston systems are in wide use.

What’s a Long Stroke Gas Piston System? 

Long Stroke Gas Piston systems (sometimes referrenced as Full Stroke) are the older of the two systems and have been quite popular in both rifles and machine guns. Long-stroke systems are in use in weapons like the AK series, the M240, and the PWS AR-15s. Classic guns like the M1 Garand used a long-stroke gas piston system. 

A long-stroke gas piston system is one in which the piston assembly travels the full distance the bolt carrier does. The bolt carrier and the piston are one conjoined series of parts. This simplifies the design and removes a few parts. 

The simplified design does tend to make weapons easier to maintain. The downside is often increased recoil due to more mass moving rearwards. 

The AK’s Long Stroke system

Is One Better Than the Other? 

This is a question that’s tough to answer. We don’t necessarily have the ability to compare like with like and make that determination. Both systems are well-proven designs with legendary weapons to their name. Modern rifles tend to be choosing short-stroke systems, but lots of long-stroke systems are kicking around and continue to be produced. 

Travis Pike
Travis Pike is a former Marine Machine gunner who served with 2nd Bn 2nd Marines for 5 years. He deployed in 2009 to Afghanistan and again in 2011 with the 22nd MEU(SOC) during a record setting 11 months at sea. He’s trained with the Romanian Army, the Spanish Marines, the Emirate Marines and the Afghan National Army. He serves as an NRA certified pistol instructor and teaches concealed carry classes.