By Adam Geibel
Due to the influx of surplus Soviet ammunition into the collectors market, some explanation of the red-tipped 7.62 mm ‘ZP’ Incendiary Ranging Round (also know as “HE-1”) is necessary so that these rounds are not inadvertently misidentified as normal tracer rounds.
The following Italian Army intelligence document was found in the United States National Archives, detailing an explosive projectile for the 7.62 x 54mm Rimmed round. Following Hitler’s offensive into Russia, the Italians dispatched an Expeditionary Corps (C.S.I.R.) in 1941 and followed it with their 8th Army in 1942.
Strictly speaking, explosive rounds smaller than .50 caliber were in violation of the Hague convention. However, specialized antiaircraft munitions fell outside of those limitations. The Italians even issued two similar armor piecing incendiary rounds for anti-aircraft work during WWII; the 7.7mm API and 12.7mm APIT. In the 7.7mm (Interchangeable with the .303 British Mk VII round) API, recognizable by it’s blue tip, the 9.96 gram projectile nose was filled with phosphorous and the 12.7mm Armor Piercing incendiary Tracer (APIT) had a 36.7 gram projectile (with both aluminum-lead oxide and magnesium-potassium chlorate antimony sulphide inside the core).
This is presented to readers as a precaution. Fulminate of Mercury that has been setting around for fifty years will be less than stable. While the likelihood of a secondary detonation in the bore is small, would you want to risk the Moison Nagant sniper you just paid $450 for?
‘ZP’ Projectile Historical Background
Since targets beyond 800 meters are difficult to hit without the aid of optics and the Soviets didn’t want to waste ammunition, they issued the ZP incendiary-explosive round for adjusting and correcting subsequent bursts of Model 1932 API-T for targets greater than 1,500 m. For closer targets, the ZP rounds were alternately spaced in the drum or belt with regular APIT or tracer rounds. It was recommended that four rounds of ball be followed by one tracer, then three ball and two ZP. During bright days, troops were permitted to increase the ratio to 3 Ball, 1 Tracer, 3ball, 2 ZP.
The primary purpose of the ZP cartridges was for anti-aircraft use from light (DP M1928) and heavy (Maxim M1910) machineguns. Special loadings of 7.62x54R were manufactured for the M1938 ‘Schkass’ aircraft machineguns, since ordinary brass and even steel cases could be damaged by these guns. In fitting the projectiles to the cases, 7.62 mm rounds were given one cannelure which required an average force of 80 kg (but not less than 40) to separate the projectile from the case. Such rounds are marked with a cyrllic ‘w’ on the case head.
The secondary use (for ranging) was considered best during the summertime or in very dry weather, when the ground was hard. These rounds would set fire to unarmored trucks, balloons/dirigibles, grass, straw, brush or light wooden buildings. It was also noted that the ZP bullet’s effect upon hitting personnel was the same as an explosive bullet (See comment on Hague Convention above). The accompanying M1932 API-T rounds were issued for use against lightly-armored vehicles (to include tankettes, armored cars and light tanks) with 5-10 round bursts recommended at longer ranges, with longer bursts at 200-300 meters or less.
As the round hits something solid, the striker and safety ring moves forward to strike the detonator cap, and sets off the explosive compound. The jacket bursts and, if in contact with fuel or other flammables, a secondary explosion ensues. Thus, the distance to the target is easier to calculate by the resulting flame and explosion.
The 7.62 mm ZP round weighed 22.2-24.45 grams, with it’s 9.66-10.36 gram (149-160.2 gr) bullet driven to 840-55 m/s (2690-2740 f/s) by 44 gr. of powder. The variation in weight and velocity gives some idea of Red Army production tolerances, yet at 140 meters, one-half of the projectiles were expected to fall within an18 cm diameter circle. Given a firing angle of 25-30”, a maximum range of 3,900 meters could be reached. With the Maxim’s sights set for the heavy ball rounds at 2,000 meters, the ZP rounds would impact at 1, 850. When using light ball rounds, the ZP would pattern at 2,400. Otherwise, ranging was normal to 1,100 m for sights set for heavy rounds and 1, 400 for light.
The Soviets published a safety note that about 5% of ZP bullets would ‘explode in the bore’, which the translators took to mean ‘shortly after leaving the barrel’, since a safety factor of 1.5 was to be applied in elevation when firing over the heads of friendly troops. Furthermore, it was noted that no one was authorized to pull apart or disassemble ZP ammunition.
While there were no special precautions against using these rounds in rifles, the “Schkass” cartridges were not recommended for use in Moison-Nagant, since the round could stick and break the extractor.
“Schkass” ammunition, made exclusively for aircraft use, had closer tolerance on propellant weight, so that there was some reasonable certainty that rounds could regularly pass through a 10 degree arc. This was in anticipation of 7.62 mm (and 12.7 mm) aircraft machineguns firing through the propeller arc. Aircraft-loaded ammunition was marked with a black propeller on the lower left hand corner of the ammunition boxes’ side.
REFERENCES: Special Ammunition for Infantry Weapons, Description and Instructions for Use (1st Edition), ORDNANCE DEPARTMENT OF THE RED ARMY, Moscow, 1940.
DISCLAIMER. This article is for historic and safety purposes only. Fulminate of mercury is a delicate chemical. Any attempts to reproduce this round would put the maker, the firer and anyone in the vicinity at risk. Furthermore, it’s probably illegal in most states and, unless you are a registered Destructive Device manufacturer, it’s stupid.
Adam Geibel, who usually writes on Armor or Cavalry topics, has been researching the Italian 3rd ‘Celere’ Division, with a book release on that unit due later this year.
|This article first appeared in Small Arms Review V2N8 (May 1999)