Your 13mm gyrojet was made from a length of copper-plated steel tubing called “Bundy” tube, which was used in the automobile industry for high-pressure hydraulic brake lines and such. It could be bent without kinking; a big advantage, and it is still in use today, mainly in air-conditioning and refrigerator systems. If you look carefully, you’ll see the soldered seam running lengthwise from the base to the tip. The tubing is formed from a flat piece of copper-plated steel rolled over into a tube shape and soldered closed. It was very cheap, which is why MBA liked it. It would also hold the pressure.
When the gyrojet case was formed, there was a small hole left at the tip, and MBA closed this by using an aluminum rivet inserted as the nose was being formed. Robert Mainhardt told me that the red tip meant nothing. It was just added on some of these to make them look different, or “sexy.” At the time, MBA was trying to sell its gyrojet firearms and rockets to collectors, and you know that cartridge collectors love color tips.
When these were being made in the late 1960s, MBA also did a lot of work on different ways of waterproofing the rockets, and one of the things they tried was to coat the base with wax, as with your specimen. This didn’t work, for a number of reasons.
Is your gyrojet’s primer snapped? Sometimes, the wax just flakes off after a few years…40 years in this case.