303 ammo

[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.