Types
There are three types of tracers: bright tracer, subdued tracer and dim tracer. Bright tracers are the standard type, which start burning immediately after exiting the muzzle. A disadvantage of bright tracers is that they give away the shooter's location to the enemy; as a military adage puts it, "tracers work both ways". Bright tracers can also overwhelm night-vision devices, rendering them useless. Subdued tracers burn at full brightness after a hundred or more yards to avoid giving away the gunner's position. Dim tracers burn very dimly but are clearly visible through night-vision equipment.
The M196 tracer cartridge (55-grain bullet) is a training round for 5.56mm NATO weapons. It has a red tip and is designed to trace out to 500 yards.
The M856 tracer cartridge (63.7-grain bullet) is used in the M16A2/3/4, M4-series, and M249 weapons (among other 5.56mm NATO weapons). This round is designed to trace out to 875 yards and has a red tip (orange when linked 4 to 1 with the M249). It is not to be used in the M16A1 except under emergency conditions and at ranges of less than 90 meters, because the M16A1's rifling twist is not sufficient to stabilize the projectile. The M16A2 rifle has a rifling twist of 1 in 7" to stabilize the M856 tracer rounds (since the M856 is slightly longer than the M196).
The M25 is a 30.06 tracer cartridge consisting of a 145 gr bullet with 50 grains of IMR 4895 powder. Orange tip. The tracer compound contains composition R 321 which is 16% polyvinyl chloride, 26% magnesium powder, 52% strontium nitrate.
The M62 is a 7.62x51mm NATO tracer consisting of a 142 gr bullet with 46 grains of WC 846 powder. Orange tip. The tracer compound contains composition R 284 which is 17% polyvinyl chloride, 28% magnesium powder, and 55% strontium nitrate. (This is the same composition used on the M196.)
The M276 is a dim tracer that uses composition R 440, which is barium peroxide, strontium peroxide, calcium resinate for example calcium abietate, and magnesium carbonate. Violet tip.
Tracer compositions can also emit primarily in infrared, for use with night-vision devices. An example composition is boron, potassium perchlorate, sodium salicylate, iron carbonate or magnesium carbonate (as combustion retardant), and binder. Many variants exist.
Read more about this topic: Tracer Ammunition
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