May 18, 2022

Inertia vs. Gas Guns – What Makes the Best Shotgun

The world of semi-auto shotguns is one that’s growing. It’s an industry that’s become more and more successful. Semi-auto shotguns are now trusted for serious work, including home defense and tactical applications. This hasn’t always been the case, but the quality of these guns has been dramatically improving. Like rifles, there are multiple operating systems out there, and with modern semi-automatic shotguns, two systems reign supreme, inertia and gas-operated systems.

Companies like Beretta, Browning, Benelli, Mossberg, and many more utilize either or even both systems. If two systems tend to dominate the market, it’s almost entirely because they each offer their advantages. Today, we will look at both systems, compare each one, and figure out what works best. Well, what works best for different situations.

What’s an Inertia System?

Inertia systems are relatively simple and quite old. Inertia systems date back to the early 1900s and a gunsmith named Carl Axel Theodor Sjögren. He created the first shotgun, and it was known as the inertial shotgun. The modern inertia systems we see in use today come from the Italian firm Benelli, which really perfected the inertia-driven system.

Inertia systems are, in many ways, a recoil-operated design, but not like the long recoil systems used by Browning in his original Auto 5. Although, the latest A5 shotguns from Browning do use an inertia-driven system. Inertia systems are really fascinating. When a weapon is fired, every part that is fixed moves rearward with recoil.

If a part isn’t fixed, it doesn’t move. The bolt and bolt body of a modern interia system is not fixed. They float, for lack of a better term. The bolt body remains still for a short period as the gun recoils. The difference between the bolt body and the movement of the rest of the gun compressors is a very stout spring. That spring is called the inertia spring and sits between the body of the bolt and the bolt head.

Once the recoil tapers off, the spring decompresses violently and flings the bolt body rearward, unlocking the bolt, ejecting the round, and cycling the weapon. This results in a semi-automatic action.

What About Gas Guns

Gas operation and gas-operated shotguns came to be a little after the second world war and the success of the M1 Garand. Gas guns are more complicated but much easier to explain. When gun powder ignites, it creates gas. That gas propels the shot or slug down the barrel. Some of that gas is bled off through gas ports.

These gas ports operate some form of a gas piston that drives the bolt rearward. This ejects the shell, cycles the action, and allows the weapon to function semi-automatically.


A big issue with semi-auto shotguns, in the beginning, was reliability. Getting semi-auto rifles to be capable and reliable is fairly easy. Getting a semi-auto shotgun to be reliable took a little more time. These days they are great, as long as you invest in a quality brand. However, between inertia and gas-driven guns, which is more reliable?

Well, that’s fairly tricky. Inertia guns run clean and cool. They don’t rely on gas to operate, so they don’t poop where they eat, so to speak. They need less cleaning and run longer between cleanings. Gas guns can choke from carbon fouling and suffer if not cleaned at least somewhat regularly.

Inertia guns are sensitive to two situations worth noting. If you load an inertia gun down with extra weight, then the gun’s recoil pattern can change and cause reliability issues. Inertia guns also require the weapon to be properly mounted and braced against the shoulder to function. If they are not properly braced, then the weapon can have feeding issues.


One of the benefits of gas-operated guns is that the pistons tend to take some of the sting out of the recoil. The gas guns eat that recoil fairly well. Inertia guns tend to recoil a bit heavier than gas guns. The difference isn’t super significant, though. You’ll feel it after a long day of shooting, but on a shot-for-shot basis, it’s less noticeable.


Different shotguns from different companies will handle them differently. It’s just a matter of the shotgun’s overall design. That being said, there are differences imparted by the inertia or gas-operated designs. Inertia guns tend to be better balanced without any distinctive weight going in one direction or the other. Inertia guns are typically lighter in weight as well.

Gas guns feature a gas system that often makes them front-heavy and a little less balanced. That’s not necessarily a bad thing, as that weight tends to make them easier to swing. It is almost always a preference issue entirely. Gas systems also tend to have fat forends as well, in case that matters to you.

What Else Do You Need to Know

There are a few benefits to both systems and a few things just worth knowing before you invest. Inertia systems do not require the adjustment of gas systems. They can handle dang near anything without the need for adjustment. Gas guns can utilize muzzle devices designed to reduce recoil without reducing reliability.

Other than that, you’ll have plenty of options in the field of shotguns. Gas guns tend to be more popular, with the Beretta-owned companies producing a wide variety of inertia guns. Both systems work extremely well and are proven in a variety of environments. Ultimately you’ll need to decide what you prioritize more in terms of recoil, ergonomics, and reliability.

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