Uk .50 bmg api

Sent to me for clarification…

Two M8 API rounds, both silver tip, both with the EXACT same headstamp. One with a single knurled ID cannelure, the other with twin knurled ID cannelures. K 75 50 headstamp. See attached pix.

Are there differences in British service API of that era, Mk1, Mk2, etc?

I checked Labbetts’ references, they don’t appear to cover production that late.


I’m fairly sure there was only the Mk1z until the very much later and current API, MP ect


When did the UK stop including the load in the headstamp?

Honestly not too sure but information from a 2006 dated A&ER document by this time the UK were using:-
M33 ball
M17 tracer
L1A1 MP (Multi Purpose)
L3A1 MPT (Multi Purpose Tracer)

one other thing to take into consideration is that Kynoch was not a ROF and did fairly much what they wanted and often used UK style military headstamps on ‘private’/ overseas contracts.

Sorry Mayhem, I missed the point of your question.
For some reason UK 50 cal was rarely,if ever, marked with the load code other than the Mk number on pre L number designations, I only know of ‘K.55 .50.G.6.Z’ tracer and there are doubts if this was ever manufactured for a UK military contract.


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On checking Peter’s Technical Ammunition booklet (Labbett / Brown, 1991) on the .50”, he states the knurled ring identification for the API was supposed to be one ring, and that the two knurled rings were meant to indicate MG Observing (L11A1, L11A2, & L13A1) and the M17K tracer. He gives four rings for the G Mk6 Tracer, and three rings for AP & AP / HC (Hardcore).

Here’s a selection of British .50” to show the different number of knurled rings.

From the top:- U/K dark purple tip (2); L11A1 MG Observing (2); L11A2 MG Observing (2); L13A1 MG Observing (2); M17K Tracer (2); AP/HC (3); G.6.Z Tracer (4)

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Muskey, the top one is unknown. I got this right?

That’s right EOD. It’s got a really dark purple / violet coloured tip, so it should be some sort of experimental. I may try to get it X-Rayed.

Sounds interesting!
Let us know when you’ll find out more.

Is the Green/Silver APHC or APHCI?

With the British round it just indicates APHC.

Apologies, my last answer was due to a misreading by me several years ago. I’ve re-examined my documents after you raised the question. Eley Ltd started looking at APHC .50” development in 1981, using inert meal as a tip filler. In 1984 they substituted the filler with incendiary composition. This variant had a green and silver tip, whereas the inert filler variant had a black & green tip. Here’s some images of the Eley Ltd HC variants (Guns Review, Aug 1986), and the bullet in question.

Will do Alex. There sounds like a normal full charge of propellant in it, and a 1962 headstamp shown below. This post relates to the dark violet tipped round.

Originally I thought the violet tipped round might be the XL6E1, a low pressure experimental version of the L11A1 MG Observing round used to range tank fire (because of the two knurled rings and 1962 date, with this round being produced in early 1963), but then thought this unlikely as my references stated this had a mauve coloured tip. However, I then X-Rayed the questioned round beside an L11A1, an L11A2, and an L13A1. It’s clear from the X-Ray image that the violet tipped round is loaded with an L11A1 style bullet, making this very likely to be the XL6E1 experimental low pressure MG Observing round. Chamber Pressure was dropped from 24 to 21 tons per square inch, with a loss of velocity of only 65 fps on average (down from 2965fps to 2900fps) (Labbett & Brown, 1991).

These are (in order) presumed XL6E1, L11A1, L11A2 & L13A1, the first three having steel cores with the L13A1 appearing darker with a tungsten alloy core, & you can observe the long central recess in the cores for the tracer element. The barium nitrate / magnesium flash composition is in the nose portion.
An example of the recessed steel core from a fired L11A1 / A2 MG Observing bullet.