Why US speargun use square cut sear tooth and Europeans used angled teeth.

[popgun pete]

It all dates back to early speargun history, as in Europe the spring gun was first out of the blocks and set the trend for all the weapons that followed. As the shaft was pushed by a long coil spring sitting directly behind the spear the first attempt used a single-piece trigger with a trigger pivot pin below the barrel tube and as that was very unreliable the decision was then made to use a pull down sear lever in the gun. Because they wanted to avoid pushing the spear backwards when pulling the trigger they angled the retaining tooth. If you use a long enough sear lever arm then it swings on a flatter arc, but there was only so much length available in the gun’s usually alloy grip handle, thus the tooth had to be angled, but never by enough to completely eliminate the problem.

Side slotted barrel band guns got rid of the long propulsion spring, but they kept that same trigger mechanism for both them and the next weapons revolution the French band powered Arbaletes, even though it no longer had a coil spring pushing over the top of it as had been the case with the compression spring gun. Le Prieur used something similar in his “declic” trigger.

Because in the USA they never started with the spring gun they used a single-piece trigger and they only work well with a square cut tooth. Some early US spearguns used the wishbone directly on the shaft tail and thus had no sear box roof, but that type of gun did not last long as securing the spear tail with a sear box roof was a much better idea. However such guns must use a square cut shaft tail or the shaft can pop off the tooth at the wrong moment

Of course Europeans also used single-piece triggers, but they were not as easy to pull with larger band loads as the two piece pull down sear lever trigger guns were and their spears were not as universal compared with the French Arbalete shafts. In the USA most guns used shafts with square cut tails until improved euroguns arrived in recent decades as formerly the guns were considered too weak being principally designed for reef work and smaller fish.

[Spear One]

Pete, we are for fortunate to have our own speargun historian! Thanks for sharing your knowledge with us!

[popgun pete]

Originally Posted by Spear One

Pete, we are for fortunate to have our own speargun historian! Thanks for sharing your knowledge with us!

I thought that I should write it down before I forget as I am not going to be here forever and many things today we just take for granted, but they have a historical basis for being the way that they are.

[popgun pete]

There were a few spearfishermen in the USA who decided to follow the pull down sear lever used by the Europeans, the most notable being the Sampson gun. Another was the 1955 gun invented by Thorburn whose idea was to shoot directly from the reel with the shooting line and reel line being one and the same. His gun is interesting as it is integrated into a single tube body with bulkheads sealing some sections off as buoyancy elements, but you can see pulling the trigger will move the spear slightly backwards against the band pull. That and shooting from a reel is not a good idea as the reel spinning will add a lot of drag to the shot.

[popgun pete]

The advantage of the square cut sear tooth and matching spear tail notch is the load bearing area is much greater if the opposing faces press flatly against each other, but in practice they may not if the sear lever is tilted too far forward with the mechanism latched. Although we do not have the capacity to tune this a lot will depend on how accurately the levers were made and how horizontal the mechanism or its cassette sit inside the gun, or if the rear grip handle tilts on the gun barrel. Those keen enough could file the faces and hope most of their spear tail notches were cut square to the shaft axis.

[popgun pete]

In Australia very early spearguns were variations on the hinge gun which uses a friction trigger, much like the tilting washer on a modern caulking gun. This means the gun has no spear tail notch and can be cocked for the shot at any insertion length, many such guns were spear tail drivers using a mid-handle with next to no gun stock and a tail cap pusher on the spear.

These guns were replaced with single-piece trigger weapons like everywhere else, and that meant square tail cut spears, same as the USA.

[popgun pete]

Note that while they look vaguely similar the Beuchat is a single-piece trigger while the Cavalero Champion gun is a two-piece pull down sear lever trigger. The Champion gun was more widely copied than the Beuchat gun was because of that better trigger. Beuchat then made a two-piece trigger gun that used a star wheel sear lever which also required using an angled tooth for its spear tail notch.

[popgun pete]

When plastic grip handles replaced cast alloy gun handles the star sear lever also made it into those guns. The leverage advantage of a star wheel trigger is zero, no better than a single-piece trigger, but it had more teeth to spread any tooth wear over.

[RichT]

great info! Thanks

[popgun pete]

To my knowledge the only star wheel sear lever that had survived into recent times are the Balco Sub “Thunder” and “Arrow” spearguns, the former has a cocking stock, and the latter does not. This gun’s trigger mechanism is actually a frame lock by courtesy of the little bump on the front of the trigger, just above where you pull on it with your finger.

[popgun pete]

Interesting to note that Sigal Sub have incorporated a floor in their Nemesis gun's sear box. You can see it here along with a spear latched in the gun.

[popgun pete]

A gun from US company Scubapro that departed from the square cut sear tooth norm is the Panther gun made from a skinned foam plastic reinforced with fiber glass and produced by injection molding. These guns use a variation on the two-piece trigger mechanism that dates back to the Undersee cam lock unit, but curiously have a rounded sear tooth. That means the spear tail is trying to jump the sear tooth, but it has no hope of doing so because the mechanism pivot pins hold the inverted U shaped sear box roof in the gun. In order to do that the pivot pins sit on the same horizontal line, normally the trigger pivot pin sits higher than the sear lever pivot.

This trigger mechanism does not obey the mechanism rules completely, but there is a reason why it works. Some of the load that would normally be transmitted to the levers is being taken by the sear box roof which means less through the levers. The trigger retention step is matched to the travel arc of the trigger, so a force component still directs to the trigger pivot pin and that is enough to keep it locked. That orange vector on the diagram shown with an X never gets big enough to shove the trigger back. Once the spear is on its way all the force is directed forwards from the bands, while at the muzzle anchor the bands try to push the gun backwards, as do all guns.

Why make the gun this way? Well it continued the lineage of a deep handle and a very long trigger as used in all the Wally Potts guns going right back to the very beginning. Still available today the Panther is a good gun and very well made. It would need to be as its injection molding dies cost a mint, enough to buy a European luxury car in its day. A very advanced gun using precision components, but only made in two sizes, a 26 inch and a 36 inch.