Newtons, pounds, joules, grams

An equipment threshold in a law has two parts: a figure and a unit. The figures are argued over all the time. The unit usually passes unnoticed, although it says what the law actually measures: the force of the bow, the energy of the arrow, its mass, the width of the head. Legal thresholds do not convert into one another; we explained why in “Which legal thresholds your bow clears”, next to the tool that compares them.

Here we follow something else: how a figure came to be written the way it is. The clearest case is Hungary, where the threshold for big game went through three units in three years. Everything below was read in the texts; where the texts are silent, we say so.

1993: fifty pounds

Hungary has allowed the bow since 1990; its road into the law is told in “A hunter without a firearm”. The first force threshold appears in the 1993 decree, at § 20: big game may be hunted with the bow only with a bow stronger than one of 50 pounds draw force (font, in the Hungarian text), with an arrow suitable for big game.

Where the figure of 50 comes from is not written in the decree, nor in any of the other texts we read.

1995: 22.7 kiloponds

In November 1995 the government tabled the bill for a new hunting act. The threshold is there, in art. 67 (2), with the species named: red deer, fallow deer, mouflon, wild boar and roe deer may be taken only with a hunting bow of a draw force above 22.7 kiloponds. That is what the government bill says.

The kilopond is the force with which the Earth pulls a mass of one kilogram; it is an old unit that measures force in “kilograms”. Fifty pounds is 22.68 kilograms, and 22.7 is the rounded figure. The arithmetic is ours: the bill does not say it converted the 50 pounds of 1993, but the figures match.

The kilopond stayed throughout the debate. One amendment asked for sika deer and Dybowski’s deer to be added to the list of species and kept the 22.7 kiloponds. Another asked for the whole paragraph to go; its story is in the article about the bow’s road into the law.

The committees’ recommendation for the detailed debate, of May 1996, keeps the kilopond too.

1996: 222.7 newtons

In its adopted text, the 1996 act says something else at § 67 (2): the bow must have a draw force above 222.7 newtons. Same rule, same species, different unit. The newton is the unit of force in the International System.

Where and why the kilopond became a newton we did not find. All the parliamentary documents we read, the bill, the amendments and the committees’ recommendation, say kilopond. The adopted act says newton.

The conversion has a detail too. These are our calculations, not a text’s:

• a kilopond is, by definition, 9.80665 newtons, so 22.7 kiloponds make 222.61 N;
• with the acceleration of gravity rounded to 9.81, the same 22.7 kiloponds make 222.69 N, that is 222.7;
• the 50 pounds of 1993, converted straight into newtons, make 222.41 N.

The figure in the act comes out of the kilopond, then, only if someone multiplied by 9.81. We do not know who did the arithmetic, nor whether it was done that way. The differences are under one newton; we show them only because, by our arithmetic, 222.7 matches 22.7 kiloponds, and 22.7 matches 50 pounds.

One more thing: the act says above 222.7 N. And the exam regulation of 2022, for the practical shooting test, asks for a bow of at least 222.7 N. By the letter of the two texts, a bow of exactly 222.7 N is admitted at the exam but does not meet the act’s requirement for big game.

The same force, written differently

Hungary is not the only country that measures the force of the bow. What differs from one country to the next is the unit, and sometimes the word.

• Finland writes in newtons: the Finnish hunting decree, at § 20, asks for a bow whose force needed to draw it is at least 180 N.
• Slovakia also writes in newtons, but calls the quantity a “weight”: the Slovak hunting act, at § 65 (2) g), allows the bow in game enclosures with a napínacia hmotnosť, a “drawing weight”, of at least 220 N: the word is “weight”, the unit is that of a force.
• Estonia writes in kilograms: the Estonian hunting act, at § 27 (1), defines the hunting bow as a bow with a draw force of 20 to 45 kilograms. It is the only text read that sets a ceiling as well as a minimum.
• Spain writes in pounds, with the kilograms in brackets, and the regions do not convert the same way. The Andalusian regulation asks for 45 pounds (20.25 kg) for big game and 35 pounds (15.75 kg) for small game: both at 0.45 kilograms to the pound. The Murcia season order asks for 45 pounds (20.25 kg) and 35 pounds (15.87 kg): the first figure at 0.45, the second close to the exact value of the pound, 0.4536 kg. The same pound, in two lines of the same text, weighs differently.
• Tuscany writes in pounds but names the standard: the Tuscan regulation asks for 40 pounds AMO standard for roe deer and 50 for the other species, at a draw length of 28 inches. What “AMO standard” means the regulation does not say; the draw length is how far the bow is drawn.

The draw length is not a detail. A bow’s force depends on how far it is drawn: the same bow, at different draw lengths, has different forces. Of the texts above, only the Tuscan one fixes the draw length. The Murcia one says the force is taken at the archer’s draw, that is, each archer’s own. The others say nothing. And none of them says how the force is checked in an inspection.

Quantities other than force

Some laws do not measure the bow at all, but the arrow.

Denmark asks for energy and mass. The Danish weapons order, at § 5, asks for red, fallow and sika deer an arrow energy at release of at least 80 joules and an arrow of at least 33 grams. For roe deer, fox, hare and goose it asks for 40 joules and 25 grams, and 70 joules with a mechanical head. The joule measures energy, not force; energy depends on the arrow’s mass and its speed, and the order asks for the mass separately.

Estonia, besides the force of the bow, also asks for grams: at § 27 (2), an arrow of at least 20 grams, with a cutting head of at least 6.4 grams and a cutting diameter of at least 24 millimetres.

The width of the head is the quantity on which the texts agree most: all those read for the guide write it in millimetres, with cutting diameters between 20 and 25; France also accepts, instead of the diameter, a blade 40 mm long. The figures, country by country, are on the pages for Hungary, Finland, Estonia, Denmark, France and Portugal.

What we do not know

• Why 50 pounds in 1993. Neither the decree nor the later texts say.
• Where and why the kilopond became a newton, between the committees’ recommendation and the act adopted in 1996.
• How the force is measured in an inspection. No text read says, not even the Tuscan one, which at least fixes the draw length.

What the texts show is the sequence: 50 pounds in 1993, 22.7 kiloponds in 1995, 222.7 newtons in 1996. That it is the same figure, converted twice, is our reading; the arithmetic above supports it, no document says it.

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