Today’s semi-automatic shotgun world is mainly dominated by gas-operated guns. Yet a handful of brands stand apart from the crowd, offering a shotgun range based on inertia-driven mechanisms. This month’s Great Gear uncovers the differences between these two distinctly different operating systems.
Whether gas-operated or inertia-driven, every semi-automatic shotgun is a gun that is able to fire a shotshell after every trigger pull, without needing to manually chamber another round. Next to the venerable pump-action shotgun, that does need manual reloading, semi-automatics are the bread and butter shotguns in North America for upland wingshooting, wildfowling and turkey hunting. Traditionalists in Western Europe and the UK however will still stick to side-by-side or over-and-under shotguns for their more upmarket driven game shooting. In the old world, they are mostly used for wildfowling, pigeon and crow shooting, although their usage gets both more universal and widely spread the more you go south to regions like Italy, Spain and Turkey. Because of their firepower, semi-automatic shotguns are ideal for ‘big bag’ shooting you will also find in countries such as Argentina.
Before it made its way to the world of shotguns, the gas-operated reloading system was first introduced on rifles. Battle rifles to be more precise. The M1 Garand for example was one of the first rifles to bleed off a small amount of the propellant gasses of a fired cartridge, that then impinged on a long rod that drove the bolt to the rear ejecting the fired cartridge and on the rebound loading a fresh round into the chamber. Using the same idea, gas-operated shotguns bleed off gas as well when a shell is fired, although the gas ports are much nearer to the action because of the considerable difference in gas pressure between rifle and shotgun ammunition. The barrel, or chamber, will have small ports in it to collect the portion of gas to drive the gas piston. The gas pushes a ring shaped piston that uses the magazine tube as a guide. Which in turn pushes the bolt back and ejecting the spent shell, then moving back forward without the presence of the gas and picking up a new shell. All this might sound like a complex mechanism, yet it can be beautifully tucked away beneath the forearm. Both to protect it and still maintain a traditional design.
Because of the relatively few internal parts, inertia-operated shotguns are notoriously simple in design. They operate by the breech bolt being held in in the chamber with a spring. When a shotshell is fired the spring becomes depressed by the rearward inertia of the gun. This will cause the bolt to move rearward, ejecting the spent shell and picking up a fresh round from the magazine. When John Moses Browning introduced his Auto-5 shotgun in 1903, he applied this system which still lives on today in Browning’s current A5 range. In the same year the Swedish inventor Carl Axel Theodor Sjögren also same up with a inertia-driven shotgun, which was the basis for today’s Benelli inertia-operated semi-automatic shotguns. Whatever the system it stems from, all inertia-driven shotguns use recoil energy to complete the loading cycle.
PROS AND CONS
Gas-operated shotguns have been pretty much been the industry standard shotgun for the last half century. One of their biggest advantages, they produce significantly less felt recoil than other shotgun types. Thanks to the bleeding off of propellant gasses and the numerous working parts, recoil is spread out over a larger part of the shotgun and is particularly less direct than an inertia-driven shotgun. Gas-operated shotguns have the added benefit of regulating gas pressure somewhat in order to keep the gun functioning reliably but without causing excess recoil or stress on the gun. What’s more, they have the ability to reliably fire a wide variety of shotshell loads without any hiccups. The biggest disadvantage of gas-operated shotguns is you need to clean them religiously. Carbon residue will build up in all of the mechanisms and cause failures and jams if not cleaned regularly. They are also less tolerant to cold weather. Compared to inertia-driven guns, gas guns can have a tendency to foul more often as the lubrication, carbon and unspent powder residue will be less fluid and become more sticky.
Inertia-driven shotguns are by far the cleanest operating semi-automatic shotguns on the market. Because of their relative lack of moving parts, there are no special gas pistons, O-rings or gas ports to clean. Less moving parts and less need for cleaning equal higher reliability. The big disadvantage of inertia-driven shotguns compared to gas-operated guns is recoil. Recoil in this type of shotgun has nowhere to go but backwards through the stock onto the user’s shoulder. This is why over the years, inertia-system brands have added collapsing stocks, soft combs, high-tech recoil pads and other features in order to tame felt recoil. This gun type is also less forgiving about what loads you can use since it doesn’t have the ability to selectively regulate its mechanism the way gas-operated shotguns do. Especially lighter loads can prove to be a challenge for out-of-the-box inertia-operated shotguns.
Because of the more modest amount of parts inertia-driven shotguns require, this gun type can be built into more slender, elegant designs. There is simply no need to conceal gas pistons or the like that gas-operated designs require. Inertia-driven shotguns can be built lighter, less bulky than their gas-operated counterparts. Lighter guns do imply that felt recoil increases. Those looking for a lightweight, easily handling, extremely reliable semi-automatic shotgun however, will have a hard time finding anything more suitable than an inertia-operated model.
Both gas- and inertia-operated shotguns are reliable and extremely effective tools whatever your sport is. Because every shooter’s circumstances and needs are different, when selecting a shotgun for a given task, specific preferences will no doubt surface. Whether you want a soft-shooting gas-operated gun for pigeon shooting or a lightweight, super-robust inertia-driven wildfowling piece, there surely is something on the market that will suit your needs.