鉄砲 TEPPŌ
Japanese Matchlock Guns

A Very Brief History

In the west this compound was known as gunpowder as its principle use was in firearms, which first appeared in the late 13th century. However, you will also see it referred to simply as powder, and post the introduction of smokeless powder in the late 19th century, as blackpowder.

There appears to be something of a question as to when exactly the gun first arived in Japan. It was once firmly believed that the Portuguese introduced the weapon in 1543 following the wreck of a Chinese junk carrying two gun bearing European traders on the island of TANEGASHIMA just south of the main island of 九州 KYŪSHŪ, but this may not have been quite the first.

So, first let us entertain the idea that if indeed early Japanese firearms had been like those of the Chinese, made of bronze, then they would be weak in comparison to iron or steel, requiring a great deal of metal to produce a safe and effective weapon. Alternatively, one that was light enough to be easily carried by the warrior, suffered with a poor or potencially hazardous performance. This would have been one of the reasons why, for the SAMURAI before the arrival of the Portuguese, firearms were not a major element in battle strategy. Of course the other answer could be that they did not have the gun.

The ideal material for gun barrels was iron or steel, but prior to the arrival of the Europeans the Japanese had no method for sealing the breech end of the barrel, without making it a hazard to use, presuming that they already had the knowledge of the gun. In Europe during the 14th century armourers had developed the technique of manufacturing the iron or steel screw breech plug that could be threaded in to the rear of the gun barrel. This resulted in powerful yet lightweight and portable firearms. Within six months of the arrival of the first Europeans in 1543, mass production of these new improved "Iron Guns" or TEPPŌ began, and by the end of the 16th century it has estimated that there were over 300,000 guns in Japan. A higher proportion by head of population than even in Europe. The result was that the humble ASHIGARU (light feet), the peasant infantry, could be quickly trained to function effectively on the battlefield as gunners as part of the newly formed TEPPŌTAI "Iron Gun Groups". Thereafter armies increased massively in size, with between a third and a half of troops equipped with these new iron guns, and the result was carnage.

This slaughter did not begin immediately, its use in war grew slowly over about 20 years. It seems that the Japanese were not convinced of their utility as mass weapons of war, preferring instead to use them as either diplomatic gifts, or for hunting, sometimes referring to them as TORI JŪ "bird guns".

The first to take these weapons to heart were people like the warrior Buddhist monks or SŌHEI, who in 1570 used massed gunnery against ODA NOBUNAGA. Then he in turn, in 1575, likewise used the same tactic to devastate the TAKEDA clan at the battle of NAGASHINO. The gun was thus by then central to SAMURAI strategic thinking.

With the end of the civil wars in the early 17th century, military guns were confined to their owner's castles, used for practise and only carried publicly for display in the annual marches from home to the capital EDO, a practise known as the alternate attendance system. A system designed to break the bank of any would be rebellious lords. During the closed era of the EDO period, guns were still made and sold, but they tended to be the small calibre so-called TORI JŪ "bird guns" intended for hunting. But from then until the latter 19th century, there was essentially no real development of the Japanese firearm. And when Commodore Mathew Perry and the American Navy arrived in EDO bay (modern TOKYŌ) in 1853 with the latest weaponry and demanded trade at the barrel of a modern cannon, the Japanese had no answer, but that's a different story.

Above: a very long 鉄砲 TEPPŌ, also known as a 火縄銃 HINAWAJŪ or 種子島 TANEGASHIMA.

The Guns

They were relatively simple weapons, see the diagram at the bottom of this page. Consisting of an iron or steel barrel deeply set into a full length wooden stock, fitted with an external firing mechanism or lock. This "lock", usually entirely of brass or rarely iron, was of what is known here in the West as the snapping matchlock design. A spring loaded snake like arm or claw called a serpentine here in the West, held a length of smouldering cord, the HINAWA "fire rope" or match, a finely woven cord which has been soaked in saltpetre, that is potassium nitrate solution. This burns very slowly and is used to ignite a tiny priming charge of extremely fine gunpowder stored in a lidded pan on the side of the lock plate. Firing happens when the shooter flips aside the pan cover with their thumb, squeezes the trigger, releasing the spring loaded serpentine, the burning match snaps down in to the fine priming powder, and then, part of the resulting flame passes through the Touch Hole, a vent in the side of the barrel, igniting the main charge of gunpowder. This propels a spherical Lead ball or TAMA, down the barrel and out of the muzzle towards its hapless victim.

Quality varied as ever, ranging from exquisite works of art, through to weapons that were very simple, intended for issue to the common foot soldiers serving as gunners. One type, had barrels so thin, that with continuous use in battle, they would overheat and flex, gaining the nickname of noodle guns.

In form the TEPPŌ or "Iron Gun" was very similar to the European sporting style of matchlock musket. That is it was fitted with a wooden stock that ended in just a cheek rest and grip, without any kind of butt that could be rested against the shooters shoulder. Thus the recoil was taken up by the shooter's arms, making for a lighter and more compact weapon. For the standard issue guns their barrels typically ranged from around 90cm (36") to 105cm (42") long, and the guns overall weight was circa 3kg (6.6 lbs) to 5kg (11 lbs), depending upon its calibre, that is the diameter of the barrel and it's ball. Some barrels of regular guns could be as short as 60cm (24") or so, while others could be up to 160cm (63") or longer.

The diameter of the barrel or its calibre was unlike today, not the means by which a gun was defined. Instead the Japanese like the Europeans of this era measured the size of the ball, not in units of length, but by weight. In England, the bore of a musket was described as a fraction of a pound of Lead. So, for example a 12 bore musket, fired a ball 1/12th of a pound in weight, that is 18.5mm or 0.729" in diameter. With Japanese gunnery the standard unit of measure is the MONME (匁), sometimes spelt MOMME, which equals 3.75 grams today. The equivalent of the most common English musket, the 12 bore would be a 10 MONME gun. The majority of battlefield guns were either 5, 6, 7, 8, 9 or 10 MONME weapons, that is shooting balls weighing between 18.75~37.5 grams (290~578 grains). Pistols and other small guns would often be between 1 and 5 MONME 3.75~18.75g (58~290 gr). While others were in effect hand cannons, shooting balls from 15 to 100 MONME, 56~375G (870~5,787 grains). See the table and the comparative illustrations of bullet diameters at the bottom of this article.

Surprisingly the Japanese were very lax with their sizing terminology. A 1 MONME gun, covered any weapon from the absolute smallest that a 1 MONME ball would fit, up to just below 2 MONME! So, care in use was vital. This may also be in part because there was some variation in ball sizes due to differences in the purity of the Lead used, and in the definition of the MONME. Today it is defined as exactly 3.75 grams, but in the past this could have been up to circa 3.76 grams. Not much of a difference you may say, but it will vary the size of the ammunition and the guns that use it. In this article I use the modern 3.75 gram definition, as this gives the smallest possible results, which is a good place to start.

Above: a hand held cannon known as a ŌZUTSU, meaning great barrel.

There is reportedly a 1,000 MONME ŌZUTSU that was made during the EDO era, firing a 86mm (3.4") 3.75 kg (8.25 lbs) ball. This was, I believe a novelty weapon, intended to amuse their wealthy owners. If such ammunition was seriously deployed, I suspect it was in a regular cannon, not a hand held weapon, well at least, I hope so.

Above: a TANZUTSU or matchlock pistol.

In addition to the full length muskets used by the infantry and the wall guns, there were also carbines, which are more compact weapons for mounted troops, with barrels as short as 35cm (13.77") called BAJŌZUTSU or "horseback barrel". Sometimes in texts you may find the term BAJŌZUTSU also used for pistols (TANZUTSU).

Cannon or TAIHŌ were relatively uncommon, but usually small in size, when compared to European artillery. This was due to problems in casting large quantities of bronze, and sealing large iron bores, as well as a need for easily transportable guns, remember, Japan is 80% mountains. A number of small European naval guns were acquired and adapted for use by the Japanese on the battlefield, but mainly for siege work. One interesting weapon was known as either a HIYAZUTSU, or "Fire Arrow Barrel", or a HIYA TAIHŌ "Fire Arrow Cannon". A tiny cannon used for launching signalling rockets, festive fireworks and maroons to raise the alarm at castles, but especially for launching the incendiary HIYA or "Fire Arrows" during a siege.

Some nice illustrations of large "hand cannon" ŌZUTSU, and TAIHŌ can be found HERE.

In smoothbore weapons there is a term called windage, which has two meanings:

• The first, and the most well known today is the need to adjust the sights of a weapon to allow for any cross wind that may effect the point of impact of a projectile.
  
• The second and less well known meaning is the difference between the diameter of the barrel or bore, and the slightly smaller diameter of the ball in smoothbore weapons.

A smaller ball is a vital requirement in a muzzle loaded weapon, as you have to force the ball down the tube to the bottom. If it is too tight, then you can't do this without the aid of a mallet, and possibly destroying the ball in the process. Usually, the windage was sufficient, that you could just simply drop the ball in and easily ram it home with a ramrod.This was done like this to ensure reliability and rapidity of fire, and to make an allowance for a build up of unburnt powder that would restrict the bore size. Smoothbores used for target shooting had very little windage, just enough that you could just about force it down with your ramrod. Such guns need cleaning almost after each shot. In guns with a large windage the balls could, when fired from an over-sized gun, end up rattling their way down the barrel, and spinning well off target, this was called chattering here in the West. This is why gunners were trained to line up and shoot at one another at relatively close range (circa 30~100m), as it was the only way to ensure that they would actually hit something. Balls were launched, not with someones name on them, but labelled "To whom it may concern!"

As mentioned, the other universal issue with gunpowder weapons was fouling, that is the build up of dirt, the residue of partially burnt powder in the bore, that iregularly reduced the windage, degrading performance, and often required gunners to use smaller balls as the battle progressed. Needless to say, accuracy, range and hitting power went down. An example from British history is the so-called Brown Bess musket. This was a .75" calibre weapon aka 11 Bore, but the standard issue ammunition was only .69 or 14 Bore. In a clean barrel you could have used 11 (.75), 12 (.729), 13 (.71) or 14 (.69) Bore balls. This is the largest windage I have found to date. The smallest being 0.005" of a custom made matchlock target pistol (TANZUTSU) with a calibre of .40, using a ball of .395" diameter.

Windage was and is calculated as a ratio of the ball diameter. So these two extreme examples would be: 12.5:11.5 for the larger windage necessary for a battlefield weapon, and 80:79 for a target grade weapon. To do the maths, simply take the ball diameter, divide it by the lower figure of the ratio to give the actual windage. If you then multiply the resulting windage by the upper figure of the ratio, this will give you the guns calibre.

Left to Right: a musket ball, a Minié ball, and a diagram.

FYI Incidentally, although rifling, the act of grooving the inside of the barrel of a gun originally intended to solve this problem, by giving the dirt somewhere to go, was discovered to impart spin to tight fitting bullets, thus dramatically increasing range and accuracy. This was known by the Europeans at this time, I do not yet know if such technology was available to the Japanese. However, in Europe rifled muskets, were only regularly used by hunters, as the need for zero windage, to ensure the Lead ball "bit" in to the rifling, meant that shooters had to carry a very stout ram-rod and a mallet to drive the ball down the rifled bore. This slowed the rate of fire dramatically, as well as making the gun extremely expensive. Also there was not enough surface of the ball in contact with the rifling to get its full potential. Rifles firing round ball bullets were effective out to about 300m. It was not until the introduction of the Minié Ball by Claude-Étienne Minié of France in 1848, that rifles became common on the battlefield. The Minié ball was small enough to drop down the bore, but it had a base that would expand upon firing, and thus with its extra surface gripped the rifling well. Such weapons radically changed warfare in the mid 19th century, with some rifles that could hit a man-sized targets out to 1,000m. The use of this devastating technology, together with traditional tactics, more appropriate to smoothbore guns, was the reason for the terrible casualty figures of the American Civil War (1861~1865).

These quick loading tubes are not like the similar type of cartridge used from 1586 in Europe, which was a light paper or cloth tube, that was, once empty of powder, rammed together with its ball down the bore to serve as a wad or patch. A patch was a portion of oiled paper or cloth used to make the ball fit tighter in the bore.

Next they would lift the match holder, locking it in the ready to fire position, and then using a small flask of fine priming powder, fill the pan and close its lid. The warrior would then replace the still burning match in to the jaws of the holder, thus the gun was ready to fire. This was much safer and faster than having another flask of powder for the main charge, as it ensured that the gun was not over-loaded, nor that the contents of the flask could be set off by a stray ember. A typical cartridge would weigh about 50~75 grams for a 10 MONME load, and they would have carried at least 10 or more cartridges in a "Belt Box" or DŌ, totaling about 750 grams (1.65 LBS). For those of you who know your black powder ballistics, the proceeding load would be about a 37.5 gram or 578 grain 12 bore Lead ball over a charge of about 6~6.5 grams or 90~100 grains of Fg black powder, which should produce a velocity of at least 1,000~1,200 feet per second, and quite a thump!

In Europe musketeers often resorted to employing their muskets as clubs in hand to hand fighting, whether the Japanese did this as well, I do not yet know, however they are always illustrated bearing one or two swords as their back up weapons.

Other features of Japanese guns included the use of adjustable sights. This was achieved by having a fixed blade type foresight at the muzzle, which was made with a groove down the centre, and a block with a similar slot part way down the barrel. In some designs this latter took pre-cut bamboo inserts, that provided the correct elevation for longer ranges. Some guns were made with three or even four sets of sights along the top of the barrel. The illustration at the top of this page shows troops using pre-cut strings or cords, to control the muzzle of the weapon at night, again to provide the desired elevation. Finally, period illustrations also show gunners using a cord as a sling, to carry the gun over the shoulder across the back.

The common infantry that is the peasant soldiers known as ASHIGARU, who were commanded by SAMURAI officers. Cavalry units were exclusively of the SAMURAI class.

As early as 1575, we see the ASHIGARU units using volley fire. Troops would discharge their guns in turn, by rank, so that a steady stream of death could be sent down range. The front rank fires, while the rear ranks loaded their guns, then stepped forward in to the front line to shoot. With three or four ranks of gunners, a withering hail of bullets could be unleashed.

Shown in some later 17th century manuals of war, one warrior within a musket unit would carry a pack upon their back, containing spare quick loading tubes, match and priming powder for their comrades to replenish their ammunition supply. How practical this was in battle is debatable, as fouling could render a musket useless relatively quickly, sometimes in as few as a dozen shots. However, it would serve well as a resupply point, when on the march.

In addition to the gunners themselves, the unit would have had all the usual extras, musical instruments and banners for signalling, porters, carts and horses to ship all the war and camp kit.

Above: a plate from the book " Ashigaru: 1467-1649" by Stephen Turnbull (Author) and Howard Gerrard (Illustrator), published in 2001, by Osprey Books in their 'Warrior Series' (#29), Priced at £11.99 from Amazon.co.uk.

2. "Quick Loading Tubes" or HAYAGO. Pre loaded reusable bamboo cartridge containing two wads glued to a ball, and one main charge of Corse Powder.

3. "Quick Loading Tube Belt Box" or HAYAGO DŌRAN. Carried on the right hip with at least 10 HAYAGO.

4. Gunpowder Flask or KAYAKU IRE "Corse Powder Container", for use as the main charge, when not using HAYAGO.

5. Priming Powder Flask, or KOYAKU IRE "Little Powder Container", for filling the priming pan of his gun.

6. Ball Bag of the KARASU GUCHI style "Crows Mouth/Beak" for loading balls in to his gun when not using HAYAGO.

7. Ammunition box or DANYAKU BAKO. Shown with its door open revealing four drawers. Note the iron carrying loops on top, through which a rectangular wooden pole is passed, and two porters then lift and place the pole upon their shoulders. This chest would carry spare balls, wadding, powder and match. Plus a ladle for melting Lead along with a bullet mould and other essential tools.

8. Match Cord or HINAWA "Fire Rope" 火縄

9. Ramrod or KARUKA. Stored in a tubular slot under the barrel of the gun.

10. Not shown, but every gunner would carry a pricker to clear the Touch Hole of their gun, plus a fire lighting kit to ignite their match.

Of Powder & Shot
Left: a pile of gun (black) powder. Right: a pile of musket balls.

As I understand it, like most nations the Japanese only ever used 100% pure Lead in their musket balls. It was cheap, easy to acquire, melt and to mould in to ammunition. As long as you kept the power down to a maximum velocity of about 450 metres per second (m/s) or 1,500 feet per second (fps), then the pure Lead balls performed extremely well. Indeed their relative softness made for devastating wounds, especially in larger calibres like 5 to10 MONME. Increasing the charge to improve velocity tended to rupture the barrels or destroy the balls in the bore, again due to their softness. So gunners tended to launch their balls at speeds of 245~365 m/s or 800~1,200 fps. And if you wanted to hit harder, use bigger balls.

To date I have no evidence that the Japanese ever attempted to add Tin or Antimony to their Lead mix. Adding a small amount of Tin would have provided some limited advantages to the user of a smootbore gun. Firstly it helped the metal flow more evenly in the mould, producing higher quality balls. Secondly it gave a measure of protection from Lead deposits in the barrel, and finally allowed you to increase the muzzle velocity beyond 450m/s (c.1,500 fps) up to about 600 m/s (c.2,000 fps). Although according to trials conducted by both the French and British armies in the early 19th century, the increase in velocity did not significantly improve accuracy or hitting power. But where people did do it, this came at a cost, not only was it more expensive, it also reduced the ball's effectiveness upon impact due to an increase in hardness. However these were all features that were to bear fruit with the introduction of the rifle in to general military service in the mid 19th century. But the SAMURAI era was to end shortly after in 1868.

Regarding powder, both here in the UK and across the pond in the USA there is a controversy amongst Black Powder shooters concerning the issue of measuring your powder either by weight or by volume. When not using pre-prepare devices like the HAYAGO, I have been unable to discover how the SAMURAI and the ASHIGARU gunners solved this tricky question. They had access to similar kit to our ancestors, powder flasks, measures, scales etc., but what were their solutions? On the face of it, weighing the powder is far safer, as it allows for the variations in quality, corsness etc., that will cause the powder to have different volumes. On the other hand it is very convenient to load by volume as this is far easier to do in the field compared to using weighing equipment. In the absense of evidence, we are left with examining the units of measure available to the Japanese of the era.

Corse to fine gunpowder weighs almost exactly the same as water, 1 gram per cubic centimetre. As most shooting data is discussed in the old Imperial unit, the grain (gr), this is what I will do here. So, there are 15.432358 grains to the gram, which fortunately is the average specific gravity for gunpowder. As I understand it the finest weight unit available to the Japanese in the past was the FUN 分 which was 0.375 grams or 5.78713 grains, whereas the smallest unit of volume was the SAI 才 which is 1.804 ml, and could therefore have held 27.84 grains of powder.

Based on these figures, using scales would give finer control. Typical loads for a 10 MONME gun would include around 90 grains of powder, say 3 SAI 才 or 16 FUN 分. A pistol (TANZUTSU) may only take 20~30 grains that is about 5 FUN 分 or just 1 SAI 才, which would require some care to ensure a safe load. Some of the really large hand-cannon (ŌZUTSU) may take as much as 150 grains of powder, that is almost 6 SAI 才or 25 FUN 分, boom...

Anyway, for those of you who maybe interested in exploring more about Japanese units of measure, I have thoroughly updated my article on the subject; CLICK HERE. If you spot any errors there, please do not hesitate to email me so I can fix or improve it.

Please note that the following explanatory text relates to the first of the two tables below, which shows the proposed final format. It will take a little time for me to calculate and add in all the extra data. As it is done I will take the material out of the second table and place it in the first. Eventually, the task will be completed.

In all cases the Japanese and metric figures are exact, while the Imperial numbers are approximate, having been rounded up or down, see methodology below.

Listed down the left hand side of the table are the various Japanese ball weights, starting with the 1,000 MONME ball and ending with the 1 MONME ball. The central part of each entry is divided in to three sections detailing the ball weight, diameter, upper and lower limits for windage, and the resulting calibres.

At the far right of the table is the US or British "bore" or "gauge", as used for shooting single projectiles from shotguns which are also smoothbore weapons, giving the equivalent size. This serves as a useful comparison for Western shooters. This figure is the number of balls to the pound that you get for that ball size. So, you can see that the 10 MONME ball is very similar to the western 12 bore or gauge.

Under each heading related to lengths, the Japanese equivalent, the SHAKKANHŌ system, where I have used the units called SUN 寸 (30.3mm), BU 分 (3.03mm), RIN 厘 (0.303mm), and MŌ 毫 (0.0303mm). For clarity I have included "0" values as well. This the Japanese would not have done, instead they would have restricted themselves to only the relevant units.

Be aware that the weight and size of the balls and resulting calibres would have varied due to the purity of the balls, the windage allowances and the skill of the gunmakers, we also have to take in to account differences in the definition of a MONME. This may result in an extra fraction of a millimetre, or sometimes a whole one or two for the calibre of a larger gun. I have not made an allowance for this, as it would be nothing more than pure guesswork.

As a visual guide just above the table itself I have included a row of silouettes representing musket balls drawn to scale from 1 MONME (8.6mm), through 10 MONME (18.5mm), up to 100 MONME (40mm). And then finally right at the end is the 1,000 MONME ball at 86mm, made, because they could! See also the article Measure It In Japanese, a comprehensive page on this website concerning Japanese units of measure.

Sometime over the next year, I hope to put together some examples of Japanese gunnery equipment; a gun, some ammunition and accessories for our SHŌGUN displays, either real or replica, and possibly ones that can even actually be shot.

Below the chart you will find first Notes To The Table, second a description of the Methodology used to perform the calculations, so if you wish you can check my figures. Then a diagram of the parts of a gun, followed by a glossary of gun terms. And lastly acknowledgements as Links, Books and Videos.

Finally, if anyone reading this, has any evidence, comments, observations, one way or another, please get in touch, as I would like to improve this article and most importantly its data. Meanwhile I hope you find this piece useful, or at least entertaining.

Measurements & Conversions

• Note that the word MONME, is, in some transcriptions written as MOMME.
  
• 1 MONME 匁 equals 3.75 grams (g) exactly, or 57.8713 grains (gr) approx. That is 120.96 bore/gauge/balls to the pound approx.
  
• 1 Gram (g) equals 15.432358 grains (gr) approx.
  
• 1 Grain (gr) equals 0.06479891 grams exactly.
  
• 1 kilogram (kg) equals 2.2046226 Pounds (lbs) approx, or 15,432.358 grains (gr) approx.
  
• 1 Pound (lbs) equals 453.59237 grams (g) exactly, or 7,000 grains (gr) exactly, or 16 Ounces (oz).
  
• 1 Ounce (oz), equals 437.5 grains (gr) exactly, which equals 28.349523125 grams (g) exactly.
  
• 1 Inch (") = 25.4 mm exactly.
  
• 1 Foot (') = 304.8 mm exactly.
  
• 1 Millimetre (mm) = 0.039370078740 Inches approx.
  
• 1 Metre (m) = 39.370078740 Inches approx.
  
• 1 Metre (m) = 3.2808398950 feet (') approx.
  
• The metric Specific Gravity (SG) of 100% pure Lead (Pb) is 11.345 grams per cubic centimetre. (cc)
  
• Specific Gravity (SG) of 100% pure Tin (Sn) is 5.769 grams per cubic centimetre (cc).
  
• Specific Gravity (SG) of 100% pure Antimony (Sb) is 6.697 grams per cubic centimetre (cc).
  
• Specific Gravity (SG) of a 1:10 ratio mix of Tin (Sn) and Lead (Pb) is 10.8381 grams per cubic centimetre (cc).
  
• 1 MŌ 毫 = 0.0303mm exactly, or 0.0011929" approx.
  
• 1 RIN 厘 = 0.303mm exactly, or 0.011929" approx.
  
• 1 BU 分 = 3.03mm exactly, or 0.11929" approx.
  
• 1 SUN 寸 = 30.3mm exactly, or 1.1929" approx.
  
• 1 SHAKU 尺 = 303mm exactly or 11.929" approx. That is circa 1 foot.
  
• 1 JŌ 丈 = 3.03 metres (m) exactly, or 119.29" approx. That is circa 10 feet.
  
• 1 CHŌ 町 = 36 JŌ = 109.08 metres (m) exactly, = 119.29 yards approx., or about 357.8740 feet.

• Take the Japanese ball weight in MONME and convert it in to exact grams, and then to grains. Round off the grains to 2 decimal places.^[1] NB: 1 MONME = 3.75 grams, or 57.8713 grains.
  
• Using the Round Ball Calculator, set to "Pure Lead" determine the inch calibre that matches the ball's grain weight. Use the 2 decimal places to refine the final digits of the ball's diameter. I felt it necessary because the calculator only deals in whole units of grain weight, and I wanted to be as accurate as possible.
  
• Convert the result to millimetres, and then divide this by 0.0303, the value of the finest unit of Japanese measure, the MŌ. ^[2] Round off the result to the nearest whole number ^[1], thus giving us the ball's size in Japanese units.
  
• Convert this figure in to exact millimetres by multiplying it by 0.303 and record the result. NB: it will always run to no more than 4 decimal places.
  
• Take this last figure and convert it in to inches by dividing by 25.4, and then round it off to 5 decimal places ^[1] and record the result.
  
• Determine the maximum and minimum windage for each ball by dividing its final diameter in millimetres by 11.5 for the largest, and 79 for the smallest.^[3] Take each result in turn and divide by 0.0303 and then round off to the nearest whole number. Convert these Japanese units in to the exact millimetre figures (4 decimal places) and in to inches, rounded off to 5 decimal places. Record the results.
  
• Add the ball diameter to the maximum and minimum windage values and record the results in each unit type.
  
• Finally, divide 7,000 by the ball's grain weight to determine its bore/gauge and, round off and record the result. Here I used no more than 5 digits to note the result.

[1] Regarding rounding off the digit to be excluded in a result. Round up the result when the remainder is a "5" or greater, and down when it is a "4". For example for a five decimal number entry, then 0.123456789 becomes 0.12346, whereas 7.65432109 becomes 7.65432.

[2] The reason for dividing the millimetre size by 0.0303mm that is the MŌ, is that this approach is to reflect the Japanese units of the SHAKKANHŌ system of traditional weights and measures, as these are what would have been used to measure and manufacture the guns and ammunition at the time.

[3] The resulting gun calibres are based upon the addition of first a minimum then a maximum value for windage. Remember that "windage" is the required space between ball and barrel. The minimum windage was calculated at a ratio of 80:79 which was the tightest I found in use in a smoothbore matchlock target pistol. This was a custom made TANZUTSU with a calibre of 0.40" and a ball diameter of 0.395". While the maximum was calculated at a ratio of 12.5:11.5, which was the loosest fit that I found for a battlefield musket. This was the British Brown Bess musket with a calibre of 0.75" and ball diameter of 0.69". All other weapons, including cannon, fell between these two ratios, which would have been for clean bores prior to shooting.

To calculate a balls windage divide its diameter by the lower figure of the ratio. To calculate the calibre of the gun multiply the resulting windage by the larger number of that ratio.

For Windage:
Ball diameter / 11.5 = loose windage
Ball diameter / 34.7 = medium windage
Ball diameter / 79 = tight windage

For Calibre:
Ball diameter / 11.5 x 12.5 = calibre of a gun with a loose windage
Ball diameter / 34.7 x 35.7 = calibre of a gun with medium windage
Ball diameter / 79 x 80 = calibre of a gun with a tight windage

Examples:
For windage: a 12 Bore ball of 0.729" / 34.7 = 0.021" i.e. a medium windage.
For calibre: a 12 Bore ball of 0.729" / 34.7 = 0.021 x 35.7 = 0.75" i.e. the calibre of a gun with medium windage.

Below are two tables of terms, "Table 1: English to Japanese", and "Table 2: Japanese to English". Table 1 has more detailed descriptions/explanations, where as Table 2 serves mainly as a cross referencing tool.

Where a word is in quotes, it means that the English expression is functionally the same as the Japanese. For example HINAWA 火縄translates as "Fire Rope", which is the Japanese name for Match Cord.

Words in brackets are alternate terms for the same object.

For ease of searching the web I have included the common yet incorrect spellings without acsents or vowel extensions which I have shown in lower case italics.

The data has been collected by myself from both the net, as well as numerous books, over the last thirty years or so. Treat it with caution as I neither read nor write KANJI, and I am not entirely sure of all of the spellings, but it is a start. The barrel lengths and calibres given are for guidance only, and should not be treated as gospel. If and when I ever get the chance, I would like to add the KANJI and HIRAGANA to these entries too. HIRAGANA is the Japanese phonetic script, which aids understanding of unfamiliar and specialist KANJI.

Ironically, in the last few days I found an old forum page, detailing about half of these terms. So I would like to acknowledge the TANEGASHIMA forum of the Nihonto Message Boards, for numerous corrections that I found to date. NB: I unfortunately am unable to join and partake, of what appears to be a wonderful group, but as I am blind, my computer's speech and text enlargement programs have coniption fits when trying to read such sites. I have to copy and paste the text in to a Notepad file, then edit out all the crap etc., oh what fun I have had... But then at least I am getting and spreading the knowledge.

• The difference in diameter between the larger bore of a smoothbore gun and the slightly smaller Ball. This feature is necessary to ensure that the shooter can push the Ball all the way to the bottom of the barrel. If it is too tight, it may be too dangerous to discharge the weapon.
  
• The allowance made when aiming for any cross winds, motion of shooter or target, that may effect the point of impact of the Ball.