M-21 "headlight" tracer, .50 BMG


What makes this tracer so different from others? Is it the tracer mix or the diameter of the opening at the base of the projectile? I’ve heard some folks say that the “headlight” tracers trace from the front of the projectile, not the rear “so the enemy can see them coming”!



It is correct that the M21 was specifically designed to provide a trace which was far more visible from the front than standard tracers. It was intended for bomber gunners, because it had been observed that attacking fighters were sometimes distracted by tracer rounds flying towards them.

This was achieved by drilling holes into the side of the jacket. They were below the cannelure, so not visible in a loaded round.


Here are some scans from Vo. II of HWS about the 50 BMG M21 Headlight Tracer. They had a red tip.

The first image are some experimental bullets to show the idea of the holes in the bullet jacket.

Here is the box for the T1E1 which was adopted as the M21

This is the M21 bullet:


I should have looked in the book first to save y’all the trouble! Duh!

I actually thought the origin of these tracers was post-WWII and never thought about looking in HWS.

So, the M-21 as produced did not have the holes in the side of the projectile, is that correct? Just the T-2 series?



Yes, The M21 DOES have holes in the bullet below the case mouth. I am not sure what the configuration is as I have never pilled a bullet to check.


Thanks for clarifying that. From the drawing in the book, it (the M-21) did not appear to have the holes like the T series. Any post WWII production of this round or in any other calibers?



None that I am aware of. Perhaps Keith Pagel could comment on this as he is the real expert on .50 BMG.


Actually, only the test series had the holes drilled into the projectile jacket. They found a much simpler way. They just loaded an ordinary tracer jacket with 100% IGNITER compound, instead of the usual igniter/tracer compound mix. The igniter compound burned a bright white, so bright, the target could see the incoming tracer projos even without side holes.

They used standard tracer projos, the only difference between the M21 and the other tracers was in the mixture alone. That made it virtually impossible to ID an M21 Tracer unless it came with a box.


Keith–Thanks for the clarification about the holes. It wasn’t real clear from HWS. I just assumed (always a bad thing to do) that since they did not say there were no holes, that there were. As I said I never pulled one down to check.
Hey, learning from one’s mistakes is what this forum can do very effectly. Always glad to be corrected. It makes better collectors out of all of us.


The point of your original comment is well taken. How tantalizing it is wondering which of the common red tip tracers is actually a rare M21 Headlight tracer. If there was just some way beyond the box label…