Copyright International Ammunition Association, 2008. All rights reserved.
Cartridge of the Month Decmber 2008

.50 caliber Spotter, M48
Specimens and photos courtesy of Paul Smith

This round was used in conjunction with the M40 106mm Recoilless rifle, developed in the late 1950’s. The standard load, the M48A1, is an observation/tracer. The gun that it is fired from is mounted co-axially to the 106mm weapon and is designed to have the same trajectory as the main weapon. The idea being that a successful strike by the .50 cal will mean a first round hit by the main weapon. [Due to the huge backblast from a recoilless rifle, their position is easily detected as soon as they fire. Using the spotter round enabled them to get on target with less chance of being detected. Normally, they would change position immediately after firing the main weapon. The 106mm recoilless rifles were mounted on small "wheelbarrow" type mounts, or on jeeps or on the M50 "Ontos" a lightly armored vehicle with three recoilless rifles on either side, four of them with the M8 spotting rifles attached.]


The case is based on a shortened .50 BMG and uses a flash tube. The projectile includes the detonator, the observation charge and the trace compound. The tracer is held within a steel cup and is separated from the observation charge by lead. Note the aluminum liner separating the observation charge from the gilding metal jacket. The detonator is of simple design and is shock sensitive.


There are a total of 9 components to the projectile: 1)core , 2)liner ,3)jacket ,4)tracer cup ,5)tracer seal ,6) detonator cup ,7)detonator charge ,8)tracer charge ,9)spotting charge.




The bullet tip color code for the USA load is yellow over red. Other countries ( Belgium , France , England , Japan , Netherlands , Spain , Switzerland , and others) have adopted this weapon platform and there are many variations to be found as a result.


This short .50 caliber case is known among shooters as the ".50 BAT" and is used by some in 50 caliber competition, where permitted by the rules. It is also found without the flash tube (as the M48). [Source: Ray Maketa.]

Jean Huon, Military rifle and Machine Gun Cartridges, pages 329-330.


Copyright 2008 by the International Ammunition Association, Inc. All rights reserved.

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  Revised 9 Decemberr 2008