1941 armour piercing 303


I found a 303 cartridge on the beach between Bawdsey Manor (development of radar fame) and Shingle Street (possible German raid foiled) Suffolk UK. The coast is littered with pill boxes. The case has K 1941 W1 marked on it. So it seems it is a common make, but does the W1 make it an armour piecing round? If so does anyone know if it was used by home guard, RAF or regulars? Are AP rounds common from this period? Were they normal issue? May this be left over from the abandoned raid on this part of the coast that was hushed up?
Any info would be gratefully received.


Welcome David

Yes the British code for Armour Piercing is a “W”, the “1” that it was the Mark 1, AP bullet, and the “K” means that the case was made by Kynoch. That the full year as opposed to just the last two digits was used on the headstamp means it was higher quality and to be issued to the RAF.

I think it very doubtful it was issued to Home Guard, because as I understand it Home Guard got the ‘leavings’ for the most part when it came to equipment.

As to common, I’d think relatively so, and that it would depend on the unit and mission for issue, be it RAF or regulars.

Does it have a raised “K” on the inside of the case at the bottom?

PS have you heard of Slapton Sands, Torcross & is it close?


Thank you for this Pete.
The K is right next (and to the left) of the date, not raised, the same size as the date stamp.
The site is on the east coast the other side of England to Slapton.
Winston was expecting the Jerries to land here and there were lots of defences.
There was a tank range near by at Boyton Marches and after the war lots of cold war testing of parts for bombs at Orfordness.
If it was issued to the RAF could it have dropped from a dog fight?
It probably did not have anything to do with the hushed up raid as that was in 1940, but this makes a good read if you like a bit of delving into a mystery, lots on the net about it.
I have got a case from out side a pill box down the coast at Walton on the Naze and the markings on that are of old stock that ties up with Home Guard use. I have been luck to pick them up off the beaches. I do not use a detector.


It could be for HG use, as the RAF had a “Once used, Dispose of” policy:

Once ammo had been up in the Colder atmosphere and Low pressure above 5,000 ft ( I don’t now exact Height)
the ammunition was no longer considered “Air Quality” and relegated to ground use…so when aircraft came back from a mission with unused ammo, it was taken out and new ammo provided. The returned ammo was declassed to “Ground use only” and returned to store or passed on to local units ( Airfield guards, HG, Ground Gunnery Training, etc.)

The same happened to ammo passed its “Use By” date ( usually One Year for Air Quality ammo)

Doc AV


The full year markings on .303" to signify .‘aircraft grade’ was abandoned in 1939,afterwhich all .303" ammunition was made to air service standards after which both full year and the last two digits were used on all .303" ammunition until it was ordered that from January 1st 1943 that only the two digit year numbers was to be headstamped.



Thank you Doc for this, I did not know this. I assume this no longer applies or there would be a lot of used once ammo in sheds.


Thank you Tony, again very useful information, thanks for sharing it.


The raised “K” I was asking about is inside the case and at the bottom of it, not the headstamp on the outside.
It is an empty case isn’t it? If it still has the bullet the letter will not be seen without pulling the bullet & don’t bother to do that.

Ta for the correction of the usage of the full date for aircraft grade.

Interesting that you think AP could have been issued to home guard.


Hi Pete,

Its quite corroded in there but I can’t see any letters on the inside base. There looks like two small dots less than a mm in size either side of the base.



Do you have any reference or documentation in relation to this “Once used, Dispose of” policy:?

The only ‘Use by Date’ for .303" that I am aware of, is that it was not to be used in synchronized guns after two years from date of manufacture.



Ta David, the two dots are the primer vent holes.