Smokeless Powder, WWII Tactical and Technical Trends, No. 47, June 1, 1944 (Lone Sentry)

There has been considerable discussion and comment to the effect that Japanese powder has much less flash and is more smokeless than our own. This may have been due to the fact that the only Japanese rifle encountered in the early stages of the war was the Model 38 (1905) 6.5-mm rifle, a small-bore, long-barreled, medium-velocity piece. Because of its long barrel, and its small bore this piece is practically flashless. This rifle is now being replaced in many areas by Model 99 (1939) 7.7-mm rifle, which is approximately the same length, weight and caliber as the U.S. Model 03 (Springfield) rifle. Model 99 has a muzzle flash comparable with that of the Springfield.

The following article, prepared principally by an officer in the U.S. Ordnance, summarizes some of the considerations accounting for these impressions.

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Powder is a propelling explosive used in ammunition for propelling a projectile from a gun, and for military purposes classified as a propellant, exploding at a slower rate than high explosives which are used in bombs and grenades. All propellants have a nitrocellulose base. Pyro powder (straight nitrocellulose powder) was for years the standard powder and the principal one used during World War I. This powder is highly smokeless, but produces a muzzle flash in firing. Moreover, it is hygroscopic, that is, it has a tendency to absorb moisture. After World War I it was seen to be desirable to have a smokeless, flashless, non-hygroscopic powder. Various organic or inorganic substances were added to the nitrocellulose base during manufacture to give improved qualities for special purposes. The result is our standard Ml type of non-hygroscopic (NH) smokeless powder for cannon. These powders are flashless in small and medium caliber cannon and when used in such weapons are termed flashless, non-hygroscopic (FNH).

In the case of small-arms weapons requiring higher velocities, the principle emphasis has been on securing greater and greater power. At the same time the barrel length has in some cases been reduced. In meeting these two severe conditions it has not been possible to secure completely flashless results in all small-arms weapons.

Flashlessness in powder is dependent not only upon the composition of the powder, but upon relationship between quantity of powder required as a charge, length of bore of the weapon, weight of projectile, and other details. While it might appear possible to obtain flashlessness in any weapon by merely increasing the amount of flash-reducing agent in the powder composition, such a procedure may be impracticable either because of increased smoke produced or reduction in potential of the powder.

In some cases the demand for increased velocities from cannon has required the use of double-base powder, the two bases consisting of nitrocellulose and nitroglycerin. The latter ingredient serves to boost the potential of the powder composition, so that higher velocity levels are possible with double-base powders than with single-base types such as the M1. However, the double-base powders burn at much higher temperatures and therefore cause rapid erosion of the gun barrel. Double-base powders are rendered flashless by the addition in the composition of small proportions of inorganic salts.

When nitro-cellulose powder is treated to reduce smoke and flash the powder potential is reduced. A powder charge for a given ammunition to be used in a specific weapon is adjusted to produce the required velocity within the pressure limits prescribed for the weapon in which the ammunition is fired. The burning rate of the powder must be controlled (this is accomplished through design and manufacture), in order to get the full results of the powder potential. A slow burning powder produces more propelling power than an instantaneous quick burning powder. Smokeless powders are not quite as sensitive as black powder, but should be handled with the same precautions.

Apparently there is an erroneous impression to the effect that Japanese smokeless powder is superior to the standard U.S. types. This situation needs to be clarified by considering all the factors involved and not simply the powder itself.

It is true that Japanese weapons*, particularly small-arms, give less muzzle flash than our weapons of similar bore. The cause can be found by examining the relative ballistic properties of guns and ammunition of the two countries. In general, the power (velocity and weight of projectile) of the Japanese weapons are very much less than our own. At the same time these weapons have appreciably longer barrels which makes them heavier. Both conditions, low power and long gun barrels, tend to make the control of muzzle flash comparatively easy. It may, therefore, be said that Japanese small-arms are actually less effective than U.S. weapons, except for the single item of flash.

For example, the Japanese .25 caliber (6.5-mm) rifle fires a 138-grain bullet at a velocity of only approximately 2,400 f/s and has a barrel length of 31.4 inches. The U.S. standard M1 rifle fires a 174-grain bullet at a velocity of 2,647 f/s and has a barrel length of 24 inches.

At present we prefer and actually employ superior effective fire power with greater range and velocity, even though these superior qualities are obtained at a cost of somewhat more flash.

A weapon and ammunition such as the Japanese have may be fairly satisfactory for weapons more or less designed for jungle warfare solely in close range combat, where operation is largely confined to cover and concealment. It is believed that any apparent superior results, such as complete flashlessness, from the use of smokeless powder by the Japanese is due to the quite low power of the ammunition and extra barrel length of the weapons rather than to the characteristics of the powder.

It should be realized that we could produce low-power weapons with ammunition which is just as flashless as the Japanese powder, but it would not be wise to reduce the superior military characteristics of our military weapons and ammunition for the sake of getting less flash. It is the hope that these features may be added without sacrificing the over-all essential characteristics such as power.

*Reference to Tactical and Technical Trends, No. 27, p. 39, tells about this so-called "flashless" ammunition.