303 ammo

[Roger Payne]

Thanks for that Bruce. I'm grateful. Many years ago (as a teenager & in my twenties, so it's ages ago!) I used to be quite a keen collector of both 303 & 7.92mm cartridges. Somewhere in the dark recesses of my loft I think I still have copies of both '.303 Inch' by the late Peter Labbett, & '7.92mm' (not sure if that's the exact title of the latter) by Daniel Kent. I think I'll try to dig them out & see if there's anything in them specifically relating to this topic. It's proving quite fascinating.

[old tanker]

...Winchester also loaded some in the early 80's. Wonder who it was for?
https://www.milsurps.com/images/impo.../uXX6pQc-1.jpg

A friend who was an Olin engineer said it was part of an 8 million round contract for South Africa. When Congress expanded the arms embargo the WCC 81 headstamped started showing up on the market. The Vickers loved it!!

[old tanker]

Secondly, early "con-corrosive" brews were found to be "unreliable" in extreme heat or cold and it took a fair while to do "aging" tests to see what happened in long-term storage, even under ideal conditions.

My general experience with British military surplus ammunition, and .303 in particular, regardless of where in the Commonwealth it was manufactured once it was 20-25 years old or older "click BOOM" hangfires were not uncommon. Radway Green from the early Fifties or POF from the Seventies are equally suspect. On the other hand US cal. 30 M2 ball and German 8x57 and 8x56R loaded during WW2 fire as reliably as if they were made last week.

Has anyone else found that to be the case?

[Brian Dick]

The '43 date Winchester .303 Mk.7z is loaded with non corrosive primers. Canadian Mk.7z loaded in the same time frame also has non corrosive primers. The Canadians manufactured normal cordite/corrosive primed Mk.7 up until the changeover in 1943. I still have some very clean '42 date Canadian Mk.7 that is not click-bang as it must have been stored well. It's temperature extremes that cause the primers to go bad.

All U.S. mfg. WW1 production .303 ammo was loaded with corrosive primers as far as I know.

[Bruce_in_Oz]

Here is the "recipe" for the priming mixture in a typical British Mercuric primer for .303 ammo:

Taken from Textbook of Small Arms, 1929 Edition. Page 233

Total mass of mixture; 0.6 grain

Eight parts by weight of fulminate of mercury
Fourteen parts ............. of chlorate of potash
Eighteen parts .............. of sulphide of antimony
One part .............. of sulphur
and One part ............... of mealed powder

The "mealed powder" is not defined anywhere I have looked so far, but could it be black powder milled to a fine dust, to increase the amplitude and duration of the "flash"?

Your basic non-corrosive primers use lead styphnate, barium nitrate, antimony trisulfide, powdered aluminum and tetrazene to do the job.
Note, whilst each of the basic mixture components are relatively "harmless", several of the combustion products are quite nasty, metallic lead vapour, for starters, hence the need for proper ventilation on indoor ranges and a warning about not regularly sniffing the muzzle after shots are fired.

This problem of toxic residue / "smoke" has given impetus to the rise of "non-toxic" primers. If you see cartridge cases with "NT" as a part of the headstamp, that is "Non Toxic' ammo. The primers and cases ARE different. All of the stuff I have seen uses a "Small" sized primer cup, BUT the flash-hole is slightly bigger than one sees in "normal" ammo. On first encounter, it was a bit of a mystery why a range pick-up .45ACP case would have a "small pistol" primer until I did a bit of searching online.

Some of the interesting things to be found in NT primers include compounds like potassium dinitrobenzofuroxane as a primary explosive and diazodinitrophenol as a secondary sensitization explosive.

Whilst there seems to be a fair bit of this NT ammo around, there is a lack of loading data AND the "proper" primers for reloading, so the brass just accumulates in storage boxes under the reloading bench.

[Lee Enfield]

The '43 date Winchester .303 Mk.7z is loaded with non corrosive primers. Canadian Mk.7z loaded in the same time frame also has non corrosive primers. The Canadians manufactured normal cordite/corrosive primed Mk.7 up until the changeover in 1943. I still have some very clean '42 date Canadian Mk.7 that is not click-bang as it must have been stored well. It's temperature extremes that cause the primers to go bad.

All U.S. mfg. WW1 production .303 ammo was loaded with corrosive primers as far as I know.

Regarding Canadian manufactured .303, the WW2 boxer primed is deemed to be all non-corrosive, the Berdan Primed is usually deemed to be corrosive.

Having said that, there is no guarantee that they didn't obtain US manufactured corrosive primers during the pressure of the war.


One of the more confusing aspects is that while the Dominion Arsenals & Defence Industries Limited were crown corporations, the Dominion Cartridge Company (DCCO) was a private company owned by CIL (Canadian Industries Ltd.), which was owned by ICI (Imperial Chemical Industries)...

DI/Z (Defence Industries Limited) WW2 headstamped ammo is boxer primed Non-Corrosive. DIL was a "war industry" crown corporation set up with assistance of Dominion Cartridge Company [DA, DAC^ headstamped] (a private company) which went to non-corrosive primers before WWI for their commercial loadings.

DAC^ (Dominion Arsenals) is usually NC boxer primed,

DI/V (Dominion Arsenals Verdun) ??

The Government Arsenals, and wartime factories used Berdan Primers - well into the 1950s (I have some 1958 dated Berdan primed Canadian .303 Mk7 ball). All Berdan primed .303 manufactured in Canada is "probably" corrosive primed.

[Brian Dick]

Interesting. I've never seen Canadian mfg. Mk.7, (cordite, Berdan primed), dated later than 1942. I think DI/V is Valcartier? Not sure on that one.