Gas Systems: Direct Impingement and Piston Finally Explained

Aug 19, 2022

A rifle’s gas system is one of the most important factors in rifle performance. There are two main types of gas systems for rifles – piston and direct impingement (DI). Each has its own advantages and disadvantages that make it better or worse for different applications.

In a direct impingement rifle, hot gases from the burning powder are diverted into a small tube that runs along the top of the barrel. This gas then pushes the bolt carrier group (BCG) backward, which in turn cycles the action.

Piston gas operation uses a larger diameter piston that is actuated by the propellant gasses to push the carrier back and forth, operating the action. In a piston rifle, the hot gases from the burning powder are diverted into a small cylinder that is attached to the bolt carrier group. This pressurized gas then pushes against a piston, which cycles the action.

Direct impingement systems: pros and cons


  • Ease of maintenance – since there are fewer moving parts, direct impingement rifles are generally easier to maintain than other types of rifles
  • Accuracy – direct impingement rifles can be extremely accurate, making them popular among competitive shooters
  • Weight – Lighter in weight & more compact
  • Cost – Less expensive than the piston option


  • Wear & Tear- hot gases are vented into the receiver area, which can cause increased wear and tear on the rifle over time.
  • Reliability – Because the BCG is in constant contact with these hot gases, it can heat up and cause problems with reliability and degrade accuracy over time.

Overall, direct impingement rifles are a popular choice for many shooters due to their accuracy. While they may be more expensive than other types of rifles, they can be well worth the investment for serious shooters, especially in the competitive field.

How piston gas systems compare:

Piston gas systems are more reliable than direct impingement systems, as they are less susceptible to problems caused by carbon buildup. They also tend to be more accurate, as the piston provides a more consistent seal on the barrel than the DI system’s moving parts. Piston-operated rifle systems tend to run cooler and cleaner than direct impingement rifle systems. However, piston gas systems are generally more expensive and heavier than their direct impingement counterparts and some shooters feel that they add unnecessary weight and complexity to a rifle.

So, which is a better gas system?

There is no clear consensus on which is better as each option has its pros and cons.

Direct impingement rifle systems have been around for many years, and are used by the majority of AR-15 manufacturers.

Piston gas systems were developed as an attempt to address some of the issues with direct impingement rifles.

The main advantage of a piston rifle is that it vents hot gases away from the receiver area, which helps to increase the lifespan of the rifle. Additionally, because the BCG is not in constant contact with hot gases, it does not heat up as much and, as a result, is more reliable.

However, piston rifles tend to be more expensive and less comfortable to shoot.


Ultimately, the best gas system for a rifle depends on the preference of the user. If reliability and durability are paramount, a piston gas system is likely going to be your best option. However, if weight and cost are concerns, a DI system may be the better choice.

Go to our Build Your Own Rifle page to check out our AR 9, AR 10, and AR 15 gas system options for your custom rifle build or call us today at (360) 559-6210 for more information.