13mm Gyro Jet and Tunnel Rat 45acp Section

13mm Gyro Jet and a 45acp Tunnel Rat Section
Thanks Mel Carpenter for the help at SLICS

You’re most welcome. Here are some details about the Gyrojet. Notice that at the top of the copper-plated-steel straight-wall case, just as it starts to transition to the truncated cone shape, there is a small area where the sharp edge of the case has been ground off. This cut was made to allow the rocket to chamber more easily.

The thing in the middle of the round that looks like a piece of folded paper is a piece of chemically-treated folded paper that ignites the hollow one-piece powder “grain” so that the powder burns only from the inside out and uniformly. The paper itself is ignited by the standard, off-the-shelf small pistol primer that is held in the steel base, or “nozzle” as MBA called it. The nozzle has four angled “ports” (exhaust holes) for forward thrust and spin for stabilization. (The pistol’s barrel is smoothbore.)

If you look closely, you can see two small pieces of metal, angled inward, right at the bottom of the gray powder grain. These kept the powder grain up and away from the nozzle so it wouldn’t clog the ports when fired. Again, if you look closely, you can see a very thin white layer of something inside the case right on top of the nozzle. That’s a piece of thin sticky tinfoil, placed there to waterproof the inside of the case. Otherwise, moisture could get inside through the ports. On firing, the weak tinfoil above the ports was easily penetrated by the gas pressure.

Finally, you might notice that on both sides of the nozzle, where it touches the case, there are two areas where the nozzle has been cut away so the spots look like cut-outs. This is a cannelure ring around the nozzle. MBA put them on all of its nozzles so that a matching case cannelure could be rolled in to secure the nozzle. Some rockets used them (the cannelures) but not all, like this “wadcutter” round.

A neat Gyrojet. Thanks for sharing it, and the .45 shot round.

Thanks for all detailed information on this round!