What is the grove for?

Unusual anulus a round the primmer in this head!

Is it to allow for swaging to hold the primmer in places?



This is an extra-strong circular primer crimp for rounds to be fired in aircraft machine guns. A blown primer might cause a gun jam that could not be corrected in flight. The cartridge, with its “Z” nitrocellulose, not cordite, propellant could be fired in any .30-06 weapon, and was. Remington made tons of this for the Brits.

Thanks for the reply Mel. I thought it was something like that but not 100% sure.

I am missing something…
What does the “300” mean? Is that a caliber designation for British use?
I found these .30-06, in Garand En Bloc Clips with British nonemclature.


Your box of .30 INCH cartridges is from Pakistan Ordnance Factory (POF) thus the British nomenclature.

Jack, the “.300” is the British caliber designation system like with the well known “.303”.

Yea, thought so, but at the same time… it does not represent the cartridge, just the bore size… them Brits are funny people sometimes.

We all have our national peculiarities.
By the way, the U.S. caliber .30 was the only “.300” in British service as far as I know. So the designation was unequivocal in their system.

As far as I’m aware this .300 designation was used only during WW II and on contract ammunition only from the USA. as JPleelen notes.

Cal. .30 (.30-06) production by the British military when they were making it post-war was “.30”.

We (the British), did actually manufacture small quantities during the war. The nomenclature, from its introduction, took the format (using Ball as an example) “Cartridge S.A. Ball .30 inch Mark IIZ” It would appear from the late Tony Edwards site that the stamping .300Z was confined to pre ‘Lend Lease’ contracts from Remington https://sites.google.com/site/britmilammo/-30-inch/-30-inch-ball

Specifficaly the groove was a heavy primer crimp. It was first used in WW1 for use in the Malin Aircraft Machine Gun since this arm had a tendency to blow primers. When the Marlins were taken out of storage and sent to Britain in 1940 fresh ammo with the heavy crimp was produced. The Marlins were altered for ground use in the UK. This ammo is fully interchangeable with other .300" ammo.
Hatcher mentions this as does HWS.