Semi-automatics for the people

Richard Atkins considers the strengths and weaknesses of the various forms of self-loading shotguns

The Breda 930i is a good example of an inertia operated semi-auto

Semi-automatic shotguns have been popular ever since John Moses Browning created the first truly successful semi-auto to come onto the market, the Browning Auto 5. This landmark gun was designed in 1898 and manufactured under licence by F N of Herstal, Belgium from 1902.

This gun was exactly what was required by the burgeoning American homesteaders: robustly built, reliable and just about affordable. When you tick so many boxes, you usually win!

So successful was the Auto 5 that it was still being manufactured many decades later, with several million made, not counting the myriad copies that were produced by other makers once the patents ran out. The originals and some later commemorative models now have a cult following and can fetch prices far beyond what they originally cost.

Semi-autos have been hugely popular in America ever since the Auto 5 made its mark, but across Europe and particularly in the UK they have not been so readily accepted. Even today prejudices remain about them, mainly on the safety aspect, because most cannot be broken when carrying between stands. Other shooters can feel disconcerted if the semi-auto user doesn’t follow some simple rules, like always having the breech bolt back and open breech facing forward with the muzzle pointed upward. A bright orange breech flag can also be slipped into the breech as visual certainty it cannot be fired.

There are four main methods of operation: Long recoil, short recoil, inertia and gas operated.

The long and short of it

The rotary head bolt from the Breda opposite. Note the rat’s tail extension to the rear

Long recoil is the system used by the Auto 5, and employs the simple principle of using the recoil from the cartridge fired to cycle the mechanism. In this design the breech bolt is locked into the barrel hood extension so that, when fired, the barrel and bolt are firmly locked together. The barrel and bolt are free to move fully rearward, powered by recoil energy, into the receiver, re-cocking the trigger mechanism along the way. At the end of the barrel and breech bolt’s travel, the breech bolt is unlocked from the barrel. The barrel has compressed a large spring that is wrapped around the magazine tube, which now returns it to its forward position.

As the barrel moves forward the fired case is ejected. A fresh cartridge is released from the magazine tube and the cartridge lifter is tripped, flipping upward to present the cartridge in front of the breech bolt. The bolt is then forced forward by a separate spring located in the stock, often termed the ‘rat’s tail’ (because that is what it looks like).

With the breech bolt and barrel once again locked together, and a fresh cartridge in the chamber, the cycle is ready to be repeated until no more cartridges remain in the magazine.

Short recoil is similar to this, but the barrel only moves back a short distance, and imparts some of its energy to the breech bolt. The barrel’s travel is then arrested, while the bolt unlocks and continues travelling backwards to cycle the mechanism in the same way as the Long recoil system. The Beretta UGB two-shot semi-auto operates in this way.

Recoil in amazement

Gas operated guns like the Winchester Super X-1 offer shooters several advantages

Inertia operated semis also rely on the recoil energy of the cartridge, but the barrel is fixed and only the breech bolt travels backwards. As with most other guns, the breech bolt is solidly locked to the barrel extension hood when the cartridge is fired.

The bolt is in two main parts; the heavy portion at the rear tries to remain stationary while the rest of it is driven sharply backwards by the recoil of the fired cartridge. Between the front and rear parts of the breech bolt is a very powerful spring that is compressed by the recoiling gun as the rear of the bolt is forced into the front section. As the spring is compressed it rotates; a cam and pin unlocks the front of the rotary head breech block from the fixed barrel. The energy now stored in the spring forces the entire bolt back to cycle the action.

What a gas

Here we see the piston that converts the expanding gas into mechanical energy. Note the sealing rings just behind the ports

Gas operation is a popular and simple system, although it comprises more moving parts than the inertia design. A small amount of the propellant gas produced by the fired cartridge is diverted, via ports in the lower barrel, into a small cylinder welded to the underside of the barrel. A piston inside the cylinder is connected to the breech bolt. As the wad passes the gas port, the piston is pushed backwards, unlocking the breech bolt and driving it backwards to cycle the action and cock the trigger mechanism. Some designs then use a spring around the magazine tube to re-engage the breech block with the (fixed) barrel. Others retain the time-honoured rat’s tail bolt extension with the spring in the stock. Both systems have there own characteristics but have each proven reliable.

All these designs owe at least something to the original John Moses Browning design; whether recoil or gas energy is used, the cartridge lifter feeding from a magazine tube and re-cocking the trigger mechanism remains a common feature.

Reasons to go semi-auto

The barrel hood has a breech locking lug recess, contributing to the strength of the design

There are some seriously good reasons for choosing a semi-auto. Especially as one gets older, one of the major potential benefits is the smoother shooting characteristics to they offer (more-so with some than others). The method by which a gun’s semi-auto mechanism is operated, combined with its weight, determines the degree of smoothness a particular model offers.

All the main operation types affect the way a gun feels and how it handles different cartridges. The long recoil system is no longer made, so they are relatively rare on clay ranges. Designed when 28 gram 12-gauge loads were rare, they tend to need at least 32 gram cartridges to cycle reliably.

Short recoil guns may not be as versatile as as gas or inertia guns when it comes to the loads they can cycle well, but when designed for a particular cartridge, like the clay target specialist Beretta UGB, short recoil operation can be very reliable indeed. Although they will cycle heavier loads, doing so can cause the action to cycle faster than intended and increase the load on some parts. This can lead to premature wear, so it is best to use such guns with the ammunition they were designed for.

Inertia operated guns tend not to get as dirty inside as gas operated guns, which can suffer from build-ups of residue from the burning propellant they use to cycle their mechanisms. Reliability of cycling can be an issue though, particularly if unsuitable ammunition is used. The latest designs have improved the range of ammunition that will cycle reliably, but issues still arise, particularly at the lower end of the shot loads. When there is only the inertia produced upon firing to compress the spring, the cartridge must produce sufficient momentum to operate the mechanism.

A typical problem comes up on clay shooting forums from time to time. A dad has an inertia operated gun that he finds works well for clays. He takes his young daughter shooting and she wants light loads to start with. Dad tries some 21 gram cartridges, but they won’t cycle the action, so he tries some reasonably soft 24 gram loads. He finds these work well for him, but when his daughter tries the same cartridges in the same gun they prove hit and miss when it comes to cycling the action. The reason is that the young lady isn’t as heavy or strong as her dad, and can’t hold the gun so firmly. The effect is that the whole gun moves back more readily and so less inertia is available to compress the spring in the breech bolt. Some have had a similar issue after adding weight to a fairly light inertia gun to reduce its recoil. Being heavier, the whole gun recoils back more slowly and fails to generate enough momentum to cycle reliably.

There is a fine balance to be struck between reliable cycling and manageable recoil. Recoil is essential for inertia guns to work, but if the gun is too light then it will kick more. This is the inherent dilemma with any inertia operated shotgun. Some makes and models are more forgiving than others, but when choosing an inertia model it’s still best to focus on a single purpose, be that 28 gram loads for clays or 34 gram plus for field use.

When the Remington 1100 set new standards for smooth shooting characteristics, excellent handling and a user-friendly trigger release, the scene was set for more gas-operated shotguns being used for clay shooting. The ‘Remmy’ 1100 was the first such semi-auto to hit the headlines in UK clay shooting (long after being established in America) when a young Duncan Lawton won a host of major championships using one. What the Remmy 1100 showed so well was that an inexpensive, machine-made semi-auto could provide pointability and handling comparable with a rather more expensive O/U gun.

The single barrel, fitted with a raised and ventilated top rib, gave the single sighting plane that allowed the O/U to take over from the side-by-side for clay target shooting, without excess forward weight. It could be made with masses of strength and still be much lighter than an O/U’s two barrels. With a steel receiver to put weight in the shooter’s hands and a long forend with a steel magazine tube and end cap it was possible to make gun that felt good and handled excellently.

The success of the Remington 1100 made other makers take note, and since then Winchester, Mossberg, Beretta, Browning, Fabarm and others, have all produces some really nice gas-operated clay target guns. The latest models are much more refined, with adjustable stocks, adjustable raised and ventilated ribs, balancing systems and more.

Softly, softly

Look closely and you’ll see the cylinder’s twin
gas ports, which divert energy to cycle the action

It is the inherently soft shooting characteristics of the gas operated semi-automatic shotgun that sets it apart. Not all are quite so soft as the Remington 1100, which is still a benchmark that other semi-autos can be judged against.

The way the gas system works extends the time the recoil force is applied over a longer period. This makes for a reduced peak recoil and lower perceived recoil. A well set up semi-auto is hard to match with any other system and just feels smoother to shoot with; the lower peak recoil impulse can be absorbed by the shooter without discomfort. For some shooters, whose shoulders have been battered by years of recoil, this can make the difference between continuing to shoot and not.

This smooth shooting is further enhanced by the extra weight a gas operated competition semi-auto can carry because it does not require inertia to operate. Most modern gas operated guns now have sophisticated gas pistons with some form of valve arrangement that ensures the gas reaching the operating piston is at the correct pressure for smooth operation whether firing 24 grams, 28 grams or even upwards of 50 grams of shot. Bleeding off excess gas ensures smooth shooting is retained and the working mechanism is never overloaded.

Feed problems can arise and when they do they are often ammunition related. Mechanisms are designed to work best with cartridges of a certain length, typically 70 mm for a clay gun. Some have true 3″ chambers and might like short cases less, especially if you try 65mm cartridges. Increasingly I hear of people buying ‘Ultra-Magnum’ 12 gauge guns with the idea that they can shoot anything. They imagine they might have a trip to the Solway Firth and use the gun’s 3.5″ chamber length; 90 per cent of these guns will never see such a cartridge, and they may well struggle to feed some 70mm cases. 67mm cases are most unlikely to feed. The feed ramp cannot be correct for all cartridge lengths to be presented correctly!

Each to their own, of course. Personally I find gas operated guns very pleasant to shoot with and perfectly reliable with the correct ammunition. Yes, the firing residues within the gas system mean they require more frequent cleaning. But this really is not very difficult or arduous. For me, it’s a small price to pay for an especially smooth shooting gun that could help keep me shooting for longer!

This article originally appeared in the June 2018 issue of Clay Shooting magazine. For more great content like this, subscribe today at our secure online store

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Posted in Features, Modern Greats, Technical

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