Here is something a little different: The primer for the 120mm separately loaded main gun on a British Challenger tank.
It appears to ba some sort of HMG round with a VERY large extractor groove and rim, which is what I thought it was when I first ever saw one on ebay when I was about 14.
It is very heavy for its size, which is understandable considering the pressures it has to handle.
It is electrically primed and has two flash holes inside the case. The primer is insulated from the case by a black plastic ring.
The headstamp is: RG PZ 79 L1A4.
Does anyone know anything about how these are loaded? I presume it is semi automatic. better still, does anyone have a photo of the Challeneger breech block? There is also a larger one of these which is similar looking which I believe was used on an earlier British tank gun system.
Here is a photo (7.62x51 Round for scale on right):
here is a photo of the Challenger tank: