Pneumatic speargun manufacturers often have slightly different ways of measuring their guns and the quoted sizes are often rounded up to give a more “marketable” number, such as 55 (for a 54) or 100 (for a 97) centimetre length model.
Here I am proposing a set of dimensional parameters that operators can measure up for themselves and use for discussions when comparing guns based on their physical characteristics rather than their performance characteristics. Particularly when trying to estimate their capability in have the necessary reach for muzzle loading the gun and whether they may need to select a shorter weapon or make use of an extension loader if their physical reach falls short of the “SLL Max” (please refer to the diagram).
Note I have used an "Aquatech" hydropneumatic gun for the diagram (it was the "right size" image), but for this purpose we will think of it as a pneumatic gun with a sliding inner barrel piston that the spear tail inserts into at the muzzle.
Don Paul will remember a similar discussion here a few years back, but I decided to formalize the nomenclature.
