Boxlocks, sidelocks and trigger plates - what’s the difference?

It is one of the rather strange parts of my job that I spend a lot of time looking at guns on the internet and in the flesh. I’m not particularly a shotgun-nut; I’m more interested in the aesthetics than I am the mechanics. However, being possessed of an enquiring mind, it occurred to me that there’s a lot of terminology going straight over my head, and a lot of questions that arise from that ignorance. 

What, exactly, is the difference between a boxlock and a sidelock, and why is the latter usually more expensive? What is a trigger plate? What is the difference between a round action and a round body, and why might one want either of them? When you get right down to it, what does it all mean for the average game shot?

To try to get some clarity, I spoke to Edward King of ASI, importers of Rizzini and AYA shotguns. Edward knows as much about guns as anyone I can think of, so he struck me as well-placed to guide me through the swamp of my own ignorance. I thought we had better start with the basics.

A brief history of gunmaking

Edward began by giving me a potted history of shotguns. He explained that the very first shotguns were muzzle-loading single-barrelled affairs. When second barrels were added, largely to give the shooter a greter chance of bagging their quarry, a second firing mechanism was required on the other side. The comparative ease of adding that mechanism to a gun with barrels in the horizontal plane compared to in a vertical arrangement made this the configuration of choice. “And thus was born the side-by-side shotgun,” he finished. 

These early guns were fired by means of a spark in the breech, but a significant innovation was imminent - the refinement of the firing mechanism to the point where where the hammer (or dog, still called ‘le chien’ in French) held a flint. “When the trigger was pulled, the flint was scraped, creatinig the proverbial ‘flash in the pan’ and bang went the gun.” These guns are what we know as “flintlocks.”

What is the “lock” on a shotgun?

It is here, perhaps that I need to explain what “lock” means in the context of gunmaking. Simply put, the lock, or lockwork, is the mechanism that translates the pull of the trigger into the discharge of the gun. My research suggests that the term probably arises from the early days of gunmaking, which owes a great deal to those other crafts that demand precision metalworking: watchmaking and lockmaking. The lockplate, inciidentally, is the piece of metal to which the lockwork is fixed.

The AYA Anniversary, a modern hammer gun RRP £52,034

With this morsel of knowledge, the soup of my ignorance began to clear. Edward continued: “The next big development was the self-contained cartridge: shot and propellant in the same unit, detonated by a primer. nstead of the triggerpull striking the flint, the hammer now merely strikes the arse end of a firing pin, which is still called a striker by many.”
 
Not only did this allow for loading from the breech rather  than the muzzle - and thus a greater rate of fire - but it also meant that the hammer - indeed all of the lockwork - no longer needed to be outside the gun. 

What is a sidelock shotgun?

“Gunmakers thought,” he went on, “why have the hammers outside the gun? Let’s put them on the inside of the lockplate, out of harm’s way. This was known as a “hammerless” shotgun, although that’s not really accurate, since the hammers are still there, just not on display.”

Accurate or not, the development gives me our next definition. A sidelock is a shotgun where the lockwork is attached to the lockplate, and housed within the body of the action of the gun, or as Edward puts it “The era of the double barrelled hammerless sidelock had begun.”

A AYA No.2 sidelock side-by-side RRP £10,441

What is a boxlock shotgun?

Edward continued his history lesson: “Jump to 1875 or thereabouts, when Messrs Anson and Deeley, working at the time for Westley Richards, designed a revolutionary new action, where the parts are contained inside the body (box) of the action, rather than on side plates outside the action. The boxlock has arrived! 

A Rizzini BR 550 boxlock side-by-side RRP £3,462

Is a sidelock better than a boxlock?

Well, that all depends. Fundamentally it depends on your definition of ‘better’. Let’s start by saying that boxlocks are cheaper to make. “There are fewer parts, making the process cheaper, which is why many entry level shotguns are built on boxlock actions,” Edward explained, adding: “Apparently, the trigger pulls on a s/s boxlock are less good than on a s/s sidelock, due to the length and engagement of the sears. Some people will tell you that they can discern this difference: often the same people who claim to be able to hear different colours…”

There is also a school of thought that sidelocks are more beautiful to look at than boxlocks, thanks in no small part to the elegant shape of the lockplates, and the greater surface area that this provides for the engravers to get to work on. 

What is a sideplated gun?

This being said, boxlocks can easily be fitted with sideplates - decorative metal plates attached where the lockplates would be on a sidelock, that serve no mechanical purpose. This allows the maker to create something with the look of a sidelock but the internal gubbins of a boxlock, offering improved aesthetics at a lower price.

A Rizzini BR552 sideplated boxlock side-by-side RRP £4,140

What is a trigger plate action?

Skipping forward to the early 20th century, Edward explains that gunmakers began experimenting with stacking the barrels vertically, rather than horizontally, the now ubiquitous over-and-under. “The O/U has been around for longer than one would imagine but a sense of tradition and the high cost of making o/u’s at that time meant that they didn’t really flourish. These days, of course, you don’t even get sent home from a shoot for turning up with one! I know, right?” observes Edward, a committed and unapologetic side-by-side man.

It was only in the 1970’s, when new manufacturing techniques meant that mass–produced over-and-under shotguns could be made cheaply and reliably, that more and more people start using them for game shooting, beginning the gradual transition away from traditional side-by-sides. 

A Rizzini RB (Round Body) Regal 'Deluxe' over-and-under - RRP £6,427

There are a number of actions commonly used in over-and-under shotguns though the most common are boxlocks, which we have already covered; trigger-plates, or some combination of the two.

The sharp ones amongst you will have already worked out that a trigger plate action is one where the main parts are mounted on to the trigger plate. Most modern over-and-unders use a modified form of the trigger plate lock system.

Edward adds: “Some guns have detachable trigger mechanisms: here, the trigger unit, complete with springs and hammers, drops out of the trigger plate, so that you can lose it in a ploughed field or have it nicked by a tea-leaf.”

Round action vs round body

The original ‘trigger plate’ was developed by Scottish gunmaker John Dickson & Son in the late 1800s and was a side-by-side. Referred to as a “Round action”, owing to the rounded shape of the body of the action, the guns are considered among the most elegant and graceful guns ever made.

A Rizzini Exmoor Round Body - RRP £3,742

There are a number of shotgun models on the market that are referred to as “round body”. These are different from round action guns, in that they are built on a boxlock or sidelock action, but, as the name implies, the bodies of the action have softened lines - rounded corners rather than angular ones. While this has little to no mechanical or handling impact, these guns do enjoy some of the petite elegance of a round action gun.

Does any of it matter?

It all comes down to your personal tastes, of course. If what you’re looking for in a shotgun is something that goes bang and makes pheasants fall out of the sky or turns clays to powder, then, well... not really.

If, on the other hand, you value clever engineering, or reliability or fine craftsmanship and embellishments, or for that matter, price, then you might favour one style over the others. None of these things are likely to make you a more successful shot, but they might make the experience of shooting that little bit more special or enjoyable.

This is, of course, a pretty simplified overview. Despite Edward’s desire to get into even more detail on the different ways that different gunmakers go about locking the barrels into place, and the nuances of lever design (he seemed strangely agitated about this), I think we’ll leave that for another article! If there are any other aspects of shotgun design and engineering that you’d like us to explore next, do leave a comment below!