Technica Spearguns

What do the Results Mean?

The results are presented in two graphs and a table; the example below represents two identical spearguns, Speargun #1 with two 16mm conventional rubbers and Speargun #2 with a single 16mm roller::

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The radar plot normalises the results between 0 and 1 to compare two spearguns; a bigger plot is a better result.
The results should be viewed within their limitations which are discussed in how does it work?


Penetration is how far will the spear penetrate into a fish and is measured in centimetres. Penetration decreases with range as the spear experiences hydrodynamic drag over distance; this is illustrated in the Penetration vs Range area graph. You can hover over the points in the graph to find their penetration in centimetres, else the exact values are in the numerical table.


Shaft velocity is measured in metres per second. Penetration is related to velocity, but proportional to kinetic energy. Kinetic energy is the best predictor of penetration, not velocity or momentum.


Recoil is 'free recoil' and measured objectively in joules. A lighter gun will feel a 'sharper' recoil as it will be travelling faster than a heavier gun, which would feel 'duller' as it's travelling slower despite both having the same free recoil energy. Recoil is linked to muzzle rise and accuracy issues; minimising recoil is desirable.

Load Effort

Load effort is the maximum pull force to load any single band on the speargun and is measured in kilograms. Load effort is increased when increasing the diameter or band stretch. Conversely, load effort is decreased using smaller diameter rubbers or stretching them less.

Bands 2 Load

Total number of overall bands to load; loading less bands takes less time so is preferable.

Shaft Buckling

Buckling is only shown in the radar plot when comparing two guns. There are no numerical results for buckling as the occurrence of buckling cannot be predicted. However, the buckling resistance of two spearguns can be compared. The simulator isn't yet able to consider rails or enclosed tracks, so spearguns with these features will have greater buckling resistance than indicated.

Shaft Bending

Bending is also only shown in the radar plot. There are no numerical results for bending as the occurrence of bending cannot be predicted. However, the bending resistance of two speargun shafts can be compared.


The efficiency is a percentage and compares how much of the rubber's stored energy is converted to kinetic energy in the spear. Different spearguns configurations waste different amounts of energy on recoil and band movement.

Accuracy Check

This value is only found in the numerical data table and should read '1'. This value is the algorithm checking the energy balance to ensure nothing was missed. It means nothing if it equals 1, but there is an error if it equals anything else.