Many gun users prefer the AR-15 for its customizability and reliability during different activities from hunting to home defense. The accessory options available for the AR-15 are so many it can be confusing trying to decide what to get.
One critical choice that a gun owner has to make when getting the rifle is between the two main operating systems – direct impingement or gas piston. Each bolt carrier group mechanism has its pros and cons, which a gun owner must understand before picking one over the other. Both direct impingement and gas piston serve the same purpose; they just achieve it differently.
How Direct Impingement Works
This operating system is the original design and for that reason, has a long track record to back up its reliability. The gun barrel has a small hole where propellant gas bleeds through, and then it travels through a small tube before it hits the bolt carrier group.
Then, the gas pushes the bolt carrier group back to trigger the cycling operation in the rifle, meaning a case is extracted and ejected. The spring loading action then pushes it forward, removing an unspent round and loading it into the chamber.
How Gas Piston Works
The AK-47 was the first firearm to use the relatively new gas piston technology. Just as with the direct impingement, the process begins by bleeding gasses into the barrel. The distinction is that in a gas piston, the gas is held in a separate cylinder as opposed to being passed through a tube.
A piston designed into the cylinder is pushed when the gasses bleed through, and that motion causes the bolt carrier group to move backward, resulting in cycling action. Spring-loaded action achieves a similar result as in direct impingement.
What Each System Offers
Besides its proven effectiveness over the years, a direct impingement system is easy to make, which means that the cost of the rifle is cheaper. For a consumer looking to save money on gun ownership, a direct impingement may be suitable.
The parts of this operating system are easy to find and are mil-spec standardized. This means that if a gas tube was damaged in an AR-15, the owner only needs to know the exact specs to get another one. One downside is that the recycled gases can dump other trace metals on the bolt carrier group, causing it to accumulate dirt at a fast rate. The same action causes the system to heat up considerably, so the shooter has to wait for it to cool.
The recycled gases in a piston system are significantly less compared to direct impingement, resulting in a clean bolt carrier group and consequently, fewer maintenance needs. For the same reason, the system is cooler such that the user can remove and hold it even after rapid succession firing.
The cons include, the shooter feels the recoil more than in a direct impingement system, which can mess with the accuracy of the rifle. Gas piston systems also use proprietary parts, meaning that they are not interchangeable and can be very costly to make.
The choice between a gas piston and direct impingement carrier group will depend on the preferences of the rifle owner.