.55 Boys AP, Headstamp "K.39 W.I"


This belted British round with “K.39 W.I” headstamp is about 50cal in size. Again, can’t provide scans or measurements until next week. Is it Kynoch?What is it?


It’s a .55 Boys AP round, Kynoch 1939.


Jon, many thanks. What is W.I?


W.I is the British designator for AP, Mk.I.
G is for tracer, B is incendiary, etc.


According to Municion.org, K stands for Kings Norton. I am too far away from my books to tell which one it is.


I have mine listed as being a Kynoch product. Kings Norton was usually marked KN (also on British coinage among other things).

Who or what do the marking “M.S” on the clip represent?


“W” is for tungsten core?



Dave the Boys had no tungsten core. The “W” is as said above the “AP” designator. There were “W1” and “W2” for the .55, the latter projectile was longer than the “W1”.


I have mine listed as being a Kynoch product. Kings Norton was usually marked KN (also on British coinage among other things).

Who or what do the marking “M.S” on the clip represent?



The ‘MS’ on the clip shows it to have been made by M. Meyers & Son Ltd of Oldbury in the West Midlands. They also made Enfield chargers and later in the war went under the dispersal code ‘M/175’.

Could you drop me a line, either here or by e-mail?

Happy collecting, Peter


IIRC Kings Norton left the ammo business c1919.


“W” on British AP ammo is for “Wolframite”, a Tungsten ORE, which was alloyed with Steel to make “Tungsten Steel”, which was used in the hardened steel cores of Small calibre AP ammo;
It has NOTHING to do with the Cutting Tool material, Known as Tungsten Carbide, which is a compound of Carbon and Tungsten, and is “cemented” or “Sintered” into plaques or cutting inserts for Machine tools. Tungsten Carbide is Very Hard (Krupp called it “Widia” (Wie Diamant) because its hardness approximated that of Industrial Diamonds) and shatters because of its brittleness. Totally unsuited as a AP Core material.
When used in Cutting tools, it(TC) has to be properly supported by the tool bar, and Not used for “Interrupted Cuts” which cause fracturing or shattering of the plaques. It’s best used for continuous Turning or Milling. High Speed Steel is more springy, and is almost universally used for “roughing out” of castings, and also “interrupted cutting” processes. (As any Toolmaker or Fitter & Turner will know)

The Two materials are completely different, and are often confused when speaking of AP cores.

Doc AV
AV Ballistics



You are very correct in pointing out that “Tungsten Steel” and “Tungsten Carbide” are often improperly interchanged when in reality they are very different materials. It might be of interest to some to note that the “High Speed Steel”, familiar to everyone with a set of drill bits, is very often alloyed with tungsten. The old classic T1 contains up to about 18%.

Does anyone have any references to the actual alloy compositions specified for AP cores from the various countries for SAA and larger caliber AT applications?



[quote=“DocAV”]“W” on British AP ammo is for “Wolframite”, a Tungsten ORE, which was alloyed with Steel to make “Tungsten Steel”, which was used in the hardened steel cores of Small calibre AP ammo…
Doc AV
AV Ballistics[/quote]

I would be very interested in your source for this attribution of the “W” code for British armour piercing.

The “W” code was first used for the Mark VIIW .303 AP round in WWI and followed the VIIS and VIIP AP rounds. The source of these suffix codes has never been confirmed, but there is a logical sequence using the first and last letters of the ammunition type. The VIIS probably represents “Steel” as it was the normal Mark VII bullet with a steel tip insert, and the VIIP similarly probably means “piercing” or “penetrating”. It was originally known as the “K.A.P.” round, standing for “Kynoch Armour Piercing”, but when the suffix codes were introduced it was necessary to use “P” as “K” had already been allocated to the Brock incendiary and “A” to the Pomeroy incendiary.

When Royal Laboratory Woolwich developed the VIIW with the larger diameter .250" core I believe the “W” was used to indicate “Woolwich” to differentiate it from the Kynoch round.

Since no official list exists that identifies the source of these codes they are open to interpretation, but I think there is sufficient evidence to support the theory I put forward in my .303 headstamp book, even though at the time I listed the “W” as unknown.



An uncle of my wife, now sadly no longer with us, was in the BEF prior to being evacuated from the beaches at Dunkirk.
He was in charge of the unit’s BOYS anti tank rifle. Prior to the evacuation he was in the rear guard protecting the unit’s retreat. A German tank appeared on the scene and having laid low to ambush it he and his group fired several shots at it . Result, absolutely nothing, several loud pings and not so much as a dent on the tank. Realising that discretion was the greater part of valor they took to their heels and ran, abandoning the rifle and all their kit in the process. He was twelve hours waist deep in the water before being taken off but survived to fight another day and live to a good age.
By WW2 these rifles were absolutely out of contention as an anti tank weapon yet were still issued. Why?


Normal “Delay” for Intel to trickle down to the Supply Branch and the Woodheads in Charge of Supply and tactics…
The Boys was designewd to penetrate Tanks and Armoured cars of the early 1930s and the Spanish Civil war…in the meantime, the Germans had upped their Armour Plating to resist 37mm and in some cases 57mm AT shells (solid shot) in heavy Tanks, and to resist Small calibre shot from such as the Solothurn 20 mm and the Boys/BRNO/ Maserchek, etc AT calibres. Well placed shots could still disable a Light Armoured Vehicle (Tyres of Armoured Cars, Periscopes of Light Tracked vehicles, even the Tracks themselves).

The Boys was continued in Issue, especially in North Africa, as it could be used more as “anti materiel” and “anti personell” at targets other than “Armour” such as coralled Aircraft on Runways, MG and Artillery Position, Normal Light wheeled vehicles (Trucks, scout cars etc)…whilst the British did not have a Infantry crew Served HMG ( as the US did with the .50BMG), vehicle mounted .5 Vickers were available, and were used by the LRDG (Long Range Desert Group); Boys Rifles were also used for “Potting” Italian Aircraft on the Ground ( a AP round through an Engine Cowling at a couple of Hundred Yards did wonders for the Plane’s constitution.)

Boys rifles continued to be made in Canada, for use in the Pacific, and for Lend Lease, (China and Soviet Union) to be used as “Bunker Busters” (Door Knockers) or as “Palm Tree Sniper Busters”; They served this use rather well.

Several were used (un-officially) in Korea by both US and Commonwealth Forces, as Long Range snipers (Much as the .50 Barrett rifle is used today). A batch of .50 cal.BMG Boys were assembled in late WW II for the US, for trials.(By J.Inglis, of Toronto)

At the end of WWII, most Boys rifles were either given away to “Allies” or unceremoniously crushed by armoured vehicles, burnt, and buried in the foundations of Parade Grounds. Most of todays surviving Boys rifles (BSA and Canadian made) have come from Non-British sources in the late 1970s and later.

Doc AV
AV Ballistics.


Municion.org description was corrected from Kings Norton to Kynoch to reflect your collective knowledge. Thank you, everyone.


Just to put some detail into the history, Kings Norton Metals and Munitions was absorbed into Explosives Trades Ltd in 1919 along with Nobel, Kynoch, Birmingham Metals & Munitions and others.

These eventually became Kynoch (Imperial metal Industries). Goodness knows how Munitions.org thought “K” stood for Kings Norton.