Black Powder Or Gunpowder

(Schwarzpulver in Ger, Poudre noire in Fr, Polvere nera in Ital, Polvora negra in Sp, Chornyi Porokh in Rus and Yuenyaku or Kokoshoku-yaku in Jap)

Black powder, the oldest explosive and propellant known, consists of a mechanical mixt of saltpeter, charcoal and sulfur in proportions varying with the purpose. Here, saltpeter is the oxygen producer, while charcoal is the combustible material. The object of sulfur is to make the powder readily inflammable and to form, on burning, K or Na sulfide (by reaction with K or Na nitrate) so as to prevent part of the COz from forming K or Na carbonate, which would, of course, mean a reduction in the amt of gas evolved. Sulfur also imparts the necessary tenacity and density to the powder mass(Ref 34,p 191) Historical (Rets 1,2,3,5,7,8,16,22 & 27). The exact date of the discovery of BkPdr is unknown. Some historians, such as Diego Ufano, attribute its discovery to the Chinese(in the 1st century before Christ), others to the Hindus and still others consider it of Arabian origin. It is very probable, however, that mixts similar to BkPdr were used very early by the Chinese(and perhaps by the Arabs) in the manuf of fireworks, rocket-type arrows or incendiary compns, but it was not used as a propellant in firearms, as there is no proof that these were invented before the 13th century. According to Claudius, the Romans were familiar with fireworks in the 4th century, AD and it was proved historically (Ref 16,p 32) that as early as the 7th century, the Greeks had a secret mixt which possessed props similar to those of present BkPdr. The famous Greek Fire of Kalinikos contained combustible material mixed with a substance closely resembling saltpeter in its props and through its use many naval victories were won by the Greeks against the Arabs, Turks and Russians. The secret of the compn was well guarded for about 5 centuries after its invention, but the Turks finally obtained the formula and used the Greek Fire against the Christians at the time of the 5th Crusade(1217). During the 6th Crusade(1249), the army of Saint Louis was assailed in Egypt with incendiaries thrown from ballistae, with fire tubes and with hand grenades of glass and metal, which scattered upon bursting(Ref 16,p 33). Marcus Graecus, in about 800 AD, described in detail the compn of the Greek Fire used in his time. It contained sulfur and saltpeter mixed with pitch and other combustibles. He also gives a compn of a BkPdr consisting of saltpeter, charcoal(willow or grapevine) and sulfur. Marcus Graecus' work was quoted by an Arabian physician, Mesue, living in the 9th century. Western Europe was in complete ignorance of such compns. It was sometime before 1249 that Roger Bacon, a monk living in England(1214-1292), described a mixt resembling the present BkPdr and, as far as is known, this was the first publication on BkPdr to appear in Western Europe. However, there was nothing in his writings to suggest that he contemplated the use of BkPdr for propelling missiles or as an explosive

The invention of BkPdr did not revolutionize the technique of warfare in Western Europe because there were no firearms. This situation lasted until about the beginning of the 14th century when Berthold Schwarz, a German monk living in Freiburg, described a device (an iron tube) for throwing stones a considerable distance, using BkPdr as a propelling medium. It is not certain whether this "firearm" was the invention of Schwarz, or if he only improved the already existing crude device. Although some historians, especially German, attribute to Schwarz, not only the invention of firearms, but also the invention of BkPdr, there is no proof for such a statement

Accdg to Col Hime(Ref 2), the cannon was invented in 1313 by an "unknown" German monk and was introduced in 1314. It was used in the same year at the battle of Banqockburn (Ref 8,p l)(See also under Cannon)

It may be mentioned that the manuf of firearms and of BkPdr in Russia began about 1389(Ref 15,p 255)

Notwithstanding the advantages of firearms (compared with the bow and arrow), it was not until the end of the 15th century that they became prevalent in open warfare. By the beginning of the 16th century the compn of BkPdr was well stabilized, becoming very close to the formula used in modern times, namely, saltpeter ca 75, charcoal 12.5-15 and sulfur 10-12%. Although practically no changes have been made in the compn since that time, many improvements have been introduced which resulted in the prepn of more homogeneous mixts and in powders with better ballistic props. The ballistics of firearms were also improved through mechanical design of the weapons

Until about the 17th century cannon balls were solid pieces of either stone or iron(first introduced ca 1391) and BkPdr was used only for propelling these balls. When hollow cast iron balls, provided with an opening and filled with BkPdr, were introduced, the powder began to function also as an explosive(bursting charge). After loading a hollow ball with BkPdr, a time fuse(resembling the present Bickford fuse) was inserted through the opening in the ball. Then the gun was loaded through the mouth with a propelling charge of BkPdr and after inserting the ball, the propelling charge was ignited through a hole near the breech of the gun. The burning gases from the decompn of the BkPdr ejected the ball and ignited the time fuse. After reaching the target, the fuse ignited the charge in the ball which resulted in expln and bursting of the ball into small pieces

Another great improvement in firearms was the introduction in the middle of the 19th century of rifled barrels and then later of breech-loading. The first large-scale use of rifled firearms was during the Crimean War (1855-6) by the French, British and Italians against the Russians, who still used smooth -bore firearms at that time

As the power, brisance and velocity of detonation of BkPdr are low, firearms using it were neither powerful nor of long range

The ancient compns were in powder form (from which the name "powder" is derived) and they burned with extreme rapidity. To make them slower burning, the Germans(ac-cording to some historians), as far back as the middle of the 15th century, introduced grained BkPdr. According to other sources it was in the Spanish Kingdom of Aragon that the first grained BkPdr was produced. At first the grains were irregular in shape and size, which lead to very non-uniform rate of burning. Gradually, it was learned that to obtain the best ballistics, the size and shape of the grain should be uniform. Napoleon was known to have used roughly cubical grains 8mm thick in the smaller field guns and grains about twice as thick in the larger guns. Later solid prismatic hexagonal grains of various sizes were introduced and in 1860 an American, Gen Rodman, developed (in an attempt to make BkPdr progressive-burning) perforated cake powders which consisted of large, solid, cylindrical grains(blocks) of nearly the same diam as the bore of the cannon, contg a hole about 14" in diam along the axis of the cylinder. One grain was required for each firing. This powder was sometimes called "Mammoth". For larger cannon (such as 10 & 12-inch guns), the blocks (prisms) were made in sections(discs) which were joined by means of bands of paper glued around the joint. When these single -perforated prisms were lighted, the area of the outer surfaces decreased as the burning advanced but the area of the inner surfaces increased and a high rate of gas production was maintained. The Russians, Prussians and the British soon adopted Rodman's idea for their artillery. The perforated prisms were manufd not only in large sizes,as advocated by Rodman, but also in small sizes, and such powders, especially when used in rifled guns, gave higher velocities and greater ranges than had been possible previously

In 1862-1864, Doremus, in France, introduced powders prpd by compressing the grains. The conglomerate thus formed retained the granular structure but was slower burning than grains in the loose form. This powder was used in small and medium caliber guns and proved to be satisfactory

The last two improvements in BkPdr were made in the 70's and 80's of the 19th century just before BkPdr ceased to be a war lord, the position it had occupied for nearly six centuries(from the 1st quarter of the 14th to the last quarter of the 19th century). These improvements included: a)the use of multiple perforations in the prismatic grain by means of which the burning surface was made to increase as the burning progressed, resulting in acceleration of the rate of gas production, and b)the use of a slower burning formulation called Brown Powder or Cocoa Powder (also called Chocolate Powder), introduced by the Germans in 1882(see below under Black Powder Modifications)

It is interesting to note that the first BkPdr factory established on the -Amer continent was in Mexico at the time of Hernán Cortez(16th century)(Ref 19). In the US, the first powders were manufd at Milton, Mass as early as 1675 and one year later were reported as being equal in quality to that of the best British powders

In 1857, the only major change which has been made in the compn of BkPdr was introduced in the US by Lammot duPont, who substituted the more abundant and cheaper sodium nitrate for the more costly potassium nitrate

The following table gives the approximate compns of BkPdr from ancient times to the end of the 19th century:

K Nit

Char

Sul

rate

coal

fur

China(before Christ)

72.6

19.0

8.4

Marcus Graecus(8th Cent)

67

22

11

Roger Bacon(ca 1252)

37.5

31.25

31.25

Arderne Formula(ca 1350)

66.6

22.2

11.2

Arabia(l6th Cent)

74

15

11

Brussels Formula

75.0

15.62

9.38

(BelgiumX1560)

British Govt Formula(1635)

75.0

12.5

12.5

Swedish(1697)

73.0

17.0

10.0

American Colonies(1775)

75.2

13.5

11.3

British Watson Formula

75.0

15.0

10.0

(EnglandXl781)

Military Powders in European

71-77

12.5-15

9-12.5

States (19th Cent)

Blasting Powders in Europe

62-73.5

12-19.4

14-20

(19th Cent)

Sporting Powders in Europe

75-80

12-17

8-10

(19th Cent)

Powder in United States

75

15

10

(19th Cent)

All of these improvements could not remove two props of BkPdr which render it not very desirable for use as a military propellant- low ballistic potential and production on firing of enormous amts of smoke, which quickly make the location of artillery obvious to the enemy. Its low power, brisance and velocity of detonation make it too weak for use as a bursting chge for any but cast-iron shell

With the invention, about the middle of the 19th century, of NG and NC, it became possible to produce propellants practically smokeless and of high ballistic potential. The first "smokeless" proplts(such as Austrian and British, developed betw 1864 & 1883), were not colloided. Being porous, they burned very fast and often caused gun barrels to burst. When the way was found to prep proplns as non-porous grains- by gelatinizing NC, either with alcohol [see B Poudre (invented in 1884 by P.Vieille) in this volume] or with a liq expl, such as NG see Ballistite(invented in 1888 by A.Nobel), in this volume, the use of BkPdr and of Cocoa Powder as a military proplnt was discontinued

With the discovery in the 1880's that PA (previously known for many years as an external medicine) is a very powerful and brisant expl, combined with the introduction by Turpin of new HE shells(which were/essentially the same as shells currently in use), the need of BkPdr as a bursting chge was completely eliminated. In later years, other HE's were invented, such as Explosive D (Ammonium Picrate), TNT, Tetryl, PETN, RDX, etc

Although BkPdrs are no longer used as military proplnts or as bursting charges in shells or bombs, they~are still used as proplnts in some sporting weapons. They are also used as blasting expls and for some other purposes (see below under Properties of Black Powders)

The use in Europe of BkPdr as a mining expl probably began in Saxony as early as 1613 and then in Hungary ca 1627. It was used in England since ca 1670, slightly later in Sweden, and in the American Colonies since ca 1712(Simsbury, Conn)

With the growth of the steel and coal industries in the first half of the 19th century, the use of BkPdr as a blasting expl increased tremendously until the production in the US in I860 was ca 25 million lbs per year. Production reached an all time high of 277 million lbs in 1917 but has gradually declined since that time; production in 1947 was ca 36 million lbs and in 1958 it dropped to ca 6 million lbs, of which 1% was used for blasting(Ref 33). In contrast to the figures on BkPdr, the production of dynamite in the US(mostly NG compns), used mainly in blasting operations, is currently ca 1 billion lbs annually Black Powders Containing Potassium Nitrate. The compn of most current military BkPdrs is betw the following limits: K nitrate 74-78, charcoal 12-16 & sulfur 10-12.5%. Compns of many sporting and blasting powders are betw the same limits. There are, however, some exceptions, such as some Belgian blasting powders, which formerly consisted of KNOa 70-73-5, charcoal 12.5-14 & sulfur 14-16% and a Russian blasting powder: KN03 66.6, charcoal 16.7 & sulfur 16.7%. One of the Russian sporting powders contained KN03 80, charcoal 12 & sulfur 8% Preparation (Refs 4, 16, 18 & 28). In earlier days, BkPdrs were prepd by grinding the ingredients by hand in mortars. This was superseded by the socalled Stamp Mill, such as is briefly described in Refs 16,18 & 28

Modern methods of prepn consist essentially of the following operations:

a) Grinding, Mixing and Incorporating. Char-coal(such as obtd by charring alder, willow or poplar trees) is broken up by Wheel Mills and then pulverized after adding the required amt of sulfur (high grade, commercial product), in a Ball Mill. In this operation sulfur is worked into the cellular openings of the charcoal. The dampened material is mixed with K nitrate (previously finely ground) and the moisture content adjusted to ca 4%. About 300 lbs of this mixt are placed in a Wheel Mill(such as described in Ref 11,p 46; Ref 18,p 69 or Ref 28,p 87) where the mass is processed during 3-6hrs. This operation is called Incorporation or Milling. The resulting material is called "mill cake", "clinker" or "wheel cake". It is broken into small pieces and sent to the press b) Pressing is done in hydraulic presses where the material is subjected to a pressure of ca 6,000 psi. As the operation is dangerous, it is usually conducted by remote control. The cakes are broken up with wooden tools and transported to the Corning Mill c) Corning or Granulation consists of cracking up the cake into grains of desired sizes by means of a series of adjustable rolls having corrugated surfaces. The granulated material is then passed throygh a series of mechanically-shaken screens where the particles of different sizes separate and the dust is removed. The particles kte classified according to the size of the 'screen and transferred to the Finishing House. The coarse material is passed through the rolls a second time and re-screened. The Corning Mill Dust is collected for use in fuses or in pyrotechnics. The Corning operation is the most dangerous of all the manufg operations and must be conducted by remote control d) Finishing or Polishing is accomplished by tumbling, for as long as 8 hrs, the granulated material in a wooden drum, rotating on its axis. This operation may be combined with drying which can be accomplished by a stream of hot air. If a glazed powder is desired, a small amt of fine graphite is added to the contents of the drum after the moisture has been reduced to a certain point but before the powder is too dry. The moisture content of the finished powder is ca 1%

Note: Final drying may be conducted by placing the powder on trays covered with canvas in the dry house e) Grading of powder consists of rescreening and separating into different grain sizes. The word "grade" applied to BkPdr refers to grain size, not the quality f) Blending consists of mixing various grades of powder to obtain a desired rate of burning or other props

Two processes for manufg BkPdr with modern production equipment have been developed and tested on a laboratory scale by PropellexChemical Division of Chromalloy Corp. Their final rept(Ref 35a) on the project describes the two processes(one with and the other without the use of CS2), and also briefly discusses a number of other methods suggested by M.Baer and K.Kite of PicArsn Properties: BkPdr is one of the weakest expls and belongs to the class of "low expls" or "propellants". It contains sufficient oxygen for combustion to CO and nearly sufficient for combn to C02. The outstanding characteristic of BkPdr is that it can be exploded(or rather deflagrated) by ignition, yet it is very insensitive to impact, properties which are rarely encountered together Note: The opinion is held by some that the powder does not explode but merely deflagrates with the evoln of gases and it is these gases which finally explode

The main disadvantages of BkPdr are: weakness, production of large amt of smoke and the corrosive action on metals of some of the products of its combustion. Alone, it is corrosive in the presence of moisture but not when dry

BkPdr is the slowest acting of all the common expls. When used for blasting operations it has a shearing and heaving action which tends to break the material into large, firm fragments or masses. This action derives from a relatively slow development of gas pressure, which is sustained. In order to obtain the best results, it must be closely confined. BkPdr is unsuitable, however, for gassy and dusty coal mines because it produces a hot durable flame. Because of its high sensitivity to friction, heat, spark and flame, danger of manuf and inability to perform in many types of hard -rock shooting, it has been replaced by other blasting expls(Ref 33)

BkPdrs contg approx: KNOa 74-75, charcoal 12.5-16 & sulfur 10-12.5%(including the compn KN03 74.0, charcoal 15.6 & sulfur 10.4%, described in Ref 31) may be considered to pos-sess(approximately) the following props(Refs

a)Brisance- by Kast formula B= 1.4 x10s vs 86 x 10s for TNT(Ref 11,p 95) by Sand Test-8g sand crushed by 0.40g BkPdr, vs 48g for TNT(Ref 31); 6.3 to 9.0g sand crushed(Ref 36)

b)Calorimetric Value- ca 720cal/g(Ref 34)

c)Compatibility- in the dry state it does not attack any of the common metals; attacks all of them, except stainless steel, when moisture is presentías low as 0.2%)(Ref 31)

d)Density- 1.7 to 1.89 depending on compn and compression(Ref 28,p 87; Ref 31 and Ref 34, p 191

e)Equation of Combustion: Sukharevskii & Pershakov(Ref 9) give the following equation:

74KNOa + 16C6H20(Charcoal) + 32S = 56COz + 3CH4 1- 2H2S +4R2 + 35N2 + 19K2C03 + 7K2S04 + 2K2S + 8K2S203 + 2KCNS + (NH4) C03 + 14CO + C + 3S

Stettbacher(Ref 11,p 108) gives for powder contg KN03 74.9, C 13.3 & S 11.8: 2KN03 + 3C + S = K2S + 3COz + N2

Bofors Manual(Ref 34,p 190) gives the following equation:

20KN03 + 32C + 8S = 5K2C03 + K2S04 + K2 S203 +3K2S + 2S + 11C02 + 16CO + 10N2 of which about 43% are gases and ca 57% solid residues

In TM 9-1910(Ref 28,p 86) the following equation for autocombustión of BkPdr is given: 74KN03 + 96C + 30S + 16H2 = 35N2 + 14CO ¥ 3CH4 + 2H2S + 4H2 + 19K2C03 + 7K2S04 + 8K2S2Os + 2K2S + 2KSCN + (NH4)2C03 + C + S +56 COz

See also Ref 28a(discussion on ignition and combustion reactions of BkPdr) and Ref 28d (description of experimental investigation of the laws of combustion of BkPdr at atmospheric pressure and below) i)Explosion or Ignition Temperature: 510 (O.lsec; no cap used); 490°(lsec in cap); 427°(ignites in 5sec); 356° (lO.sec) (Ref 31): 359°(12sec)(Ref 26a,p 1393); 457° (ignites in 5sec) (Ref36)

g) Flame Sensitivity- ignites very readily(Ref 20,p 37 & Ref 28,p 86): Escales(Ref l,p 394) gives for prismatic pdr 5.4 to 9-0 sec and for small grain pdr 3-6 to 4.5sec h)Friction Sensitivity by Pendulum Test- affected with steel shoe and unaffected with fiber shoe(Ref 31); no expln with steel shoe (Ref 36)

i)Heat of Combustion, Q^ ca 1425cal/g(Ref 9) j)Heat of Explosion, Q^ 665 to 690cal/g(Ref 9); 693cal/g(Ref 36)

k)Hygroscopicity gains 1.91% at 25° & 90% RH(Ref 31)

1)/gnitability, flame of a match or of a miner's squib as well as electric spark ignites it(Ref 36)

m) Impact Sensitivity: PicArsnApp, 2kg wt 16 (vs 14" for TNT) (Ref 31); Bofors Detn, 2kg wt ca 70 cm(Ref 34,p 191); B of M, 2kg wt 49cm for KN03 BkPdr and 66cm for NaNOa BkPdr(Ref 36)

Deck(Ref 6) gives 32" for BkPdr dust when detd by PicArsnApp with 2kg wt reinitiation and thermal decomposition of BkPdr is discussed by Blackwood & Bowden (Ref 28a)

o)lnternational Heat Test at 75 - 0.31% loss in 48 hrs(Ref 31)

p)Maximum Temperature of Explosion- 2380° vs 2800° for TNT(Ref 11,p 95); ca 2400°(Ref 34,p 19)

q)Power, by Trauzl Test- 30cc expansion produced by lOg sample vs 300cc for TNT (Ref 34,p 191); 10% of TNT(Ref 31); by Ballistic Mortar 50% TNT(Ref 31); by Ballistic Pendulum 42.5% of TNT for pdr contg KNOg 75.06, charcoal 13.68, S 10.76 & moisture 0.50%(Ref 36)

t)Rate of Burning depends on compn, density and grain size. The rate increases on increasing the percentage of oxidizer(such as K or Na nitrate), within certain limits. The rate decreases when the percentage of fuel(char-coal, coal, brown coal, etc) is increased. With increase in the amt of sulfur, the rate increases to a certain extent, although sulfur acts mainly as a fuel and only to a small extent as an oxidizer(because it forms K2S). The rate decreases with an increase in grain size and si decreases with increase in density. When confined, increase in gas pressure causes increase in burning rate(Ref 20,pp 37-8 & Ref 28b,pp 86-7). W.O.Snelling & W. C.Cope, USBurMines Tech Paper 6,Washington, DC(1912), give the rate of burning of fuse pdr as influenced by temp, pressure, moisture and granulation. For instance, an 80-mesh pdr burns at atm press and ord temp at the rate of 82.3sec/m(25.1 sec/ft) vs 76.3sec/m(23.2sec/ ft) for 40-60-mesh pdr. A cotton covered safety fuse burns at atm press and 18° at the rate of 82.3sec/m(25.6sec/ft) vs 49-8(15.2) at 15psi and 34.4(10.5) at 30psi(p 15). Moisture & high temps cause a decrease in burning rate. Safety fuses mfd by the DuPont Co burn either 90 or 120sec/yd(Ref 28,p 89). Some fast-burning fuse pdrs burn ca 30sec/yd, whereas some modified slow-burning pdrs, such as those contg aldol-a-naphthylamine and aldol-/3-naph-thylamine, burn at the rate of 250-300sec/yd[H. H.Holmes & W.E.Lawson,USP 2414465(1947) & CA 41,2578(1947)]. Escales(Ref l,p 396) gave for a rifle BkPdr at latm press 0.80cnV' sec & at 500atm 6cm/sec; the corresponding values for a brown prismatic pdr were 0.90 & 4cm/sec. US Army Purchase Description X-PA-PD-623 gives "static burning time" requirements for fuze pdrs when tested directly in fuzes. For instance, for fuzes M54, M55A3, M77 or M84 the average burning time shall be 18.0 to 23-0sec and the "minimum average burning time" 36.0sec. The corresponding values for M65A1 fuze are 9.0 to 13.0sec & 18.0sec. Tests for "rates of burning" of black blasting pdr and for pellet pdr are described by C.E.Munroe & J.E.Tiffany, Bur-

Mines Bull 346, "Physical Testing of Explosives", Govt PrtgOff,Washington,DC(1923). Combustion of BkPdr at atm and lower pressures was studied by A,Douillet,MP 37, 167-96(1955)

s)Sensitivity to Electrostatic Discharge (Joules) >12.5 for unconfined and 0.8 for confined sample(Ref 31)

t)Sensitivity to Flame. See Flame Sensitivity u)Sensitivity to Sparks and Incandescent Particles- very sensitive(Ref 28,p 88) v)Specific Energy(f) 2310 vs 8080 for TNT (Ref 11)

w)Specific Heat ca 0.2cal/g at RT(Ref 36) x)Vacuum Stability- 0.5rol/40hrs/100° and 0.9ml/40 hrs/120° (Ref 31); O.86m.l/40 hrs/ 120° for black meal powder and 0.75 for meal pdr contg 2% stearic acid(Ref 36) y)Velocity of Detonation- ca 400m/sec at d 1.6-1.7 vs 6825 for pressed and 6640 for cast TNT at d 1.56(Ref 31); 400m/sec at 1.7(Ref 34,p 191)

z)Volume of Combustion Gases at 0° & 760mm 271-280 1/kg vs 690-730 for TNT; ca 280 1/kg (Ref 11,p 95 & Ref 34,p 191) z ) Uses: Sporting proplnts, blasting and demolition expls, time fuses, primers, igniters(of smokeless proplnts), time rings(in fuzes), delay & relay elements, petards, pyrotechnics, base chge for shrapnel shells(now seldom used), bursting chge for blank, saluting & practice cartridges & shells, flash reducer (in some smokeless proplnts), squib charges, Navy donuts for catapult charges, smoke-puff chges, chemical ammo as well as in Rocket, JATO and missile boosters and sustainers (Ref 28b,p 86; Ref 31 & Ref 34) Black Powders, Containing Potassium Nitrate, Used in the United States of America. Requirements for the US Armed Forces are covered by the Specification JAN-P-223A for :he powder alone; JAN-P-156 for potassium litrate; JAN-C-178A(1) for charcoal(usually sbtd by burning peeled willow, alder or certain nardwoods); JAN-S-487 for sulfur and JAN-G • 155(1) for graphit«. The compn is the same :or all grades: K nitrate 74.0, charcoal 15.6 & sulfur 10.4%, but tolerances vary slightly up to ± 1.0%). The ash content for all grades s 0.80%(max), moisture 0.70% for all grades ;xcept A-l, for which the max is 0.50%, and he density is 1.72 to 1.77. No foreign matter ;uch as gritty or fibrous particles shall be >resent

For a description of various grades of US military BkPdrs and their uses, see JAN -P-223A

The compns listed above may be considered as fast-burning, while the following compn is slow-burning: K nitrate 59.0, charcoal 15.6, sulfur 10.4 & Ba nitrate 15.0%. By blending fast- with slow-burning mixts in different propns, it is possible to obtain powders suitable for various types of fuzes

Another slow-burning mixt is the so-called Coal Powder. Its compn is: K nitrate 70.0±1.0, <;oal 14.0+1.0 & sulfur 16.0±1.0%. The US Armed Forces requirements for this powder are given in Spec X-PA-PD-623(listed as Type II Powd er, Black, Slow Burning) which superseded Spec JAN-P-540. The coal used for this powder must be semibituminous and of such fineness that 100% passes through No 140 US Std sieve and not less than 45% through No 200 sieve. Other requirements for coal are: moist 0.75%(max), ash 11.0±1.5, vplatile matter 18.0±1, fixed carbon 70.5±3.5 & sulfur 3.0+0.5%; no foreign matter, such as gritty or fibrous particles, shall be present. This BkPdr shall be of such fineness that 3%(max) is retained on a No 140 US Std sieve and 2%(max) retained on a No 200 sieve. Static burning time, when loaded in US Std Fuzes M54, M55A3, M77, M84 and M65A1, must be as indicated above under Rate of Burning(item) r). No gritty or fibrous matter shall be present

A BkPdr used in US time fuzes for military ammo consists of K nitrate 74.0+1.0, charcoal 15-6±1.0 & sulfur 10.4+1.0% and the requirements of the US Armed Forces are covered by Spec X-P A-PD-623 (listed as Type 8, Powder, Fuze), which superseded Spec JANrP-TRP. The ash content 0.60%(max) and granulation must be of such fineness that 3%(max) is retained on a No 140 US Std sieve and 2%(max) passes through a No 200 sieve. When loaded in US Std Fuze M54, M55A3, M77, M84 and M65A1 the static burning time of the powder must be as indicated above under Rate of Burning(item r); no gritty or fibrous matter shall be present

BkPdrs for blasting operns by the DuPont Co are described in Ref 27,pp 45-8. Their Pellet Powder may be considered as an improved form of BkPdr

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