US .303 WRA Primer Crimp Development WWII for UK

Regarding the Winchester.303 production for the UK during World War II, I noticed what looks like a change in primer stake crimp style through 1941 production. From ones I’ve looked at, 1940 marked production has no primer crimps, 1941 production has no crimp, also three equi-distant stake crimps, and four equi-distant stake crimps. Then in 1942 (& 1943) they have four equi-distant stake crimps. So, on the face of it, these cartridges seem to have started off with no primer crimp, then it was realised they were needed so three crimps were tried before they settled on four crimps. Picture below to illustrate. Is anyone aware of any formal info on the primer crimping decision making for these cartridges? Thanks, Pete.

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Was crimping added because of aircraft use or some other reason?

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My understanding is that it was initially supplied as ‘Red Label’ for use by the RAF, but there was some unreliability issue identified at an early stage with it’s performance and it’s use was restricted to ground use only.

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It continued on to the 1943 production,
I 'm not sure why this progression was done. The early ammunition WRACo sent was considered sub-standard for issue the troops & I believe Red Label ‘grade’ was not a factor. it was just crap ammo. Not sure about production and / or acceptance for later production. No, not seen anything about this development.

But this style crimping was not unknown here in in the United States.
303 US 15 VII

Vlad, I’m sure your aware of this but a primer falling out can cause a jam in any firearm not just automatics. Plus you have the problem of possible pressure venting depending on the stage that it decides to leave the pocket. In an aircraft it’s just harder to fix the jam, and with all the moving parts more likely to screw something else up.


Fantastic - thank you Pete! Now I have a crimping variation to look for. I have not seen the wide crimps that you show. Are these commonly encountered?

Sorry Mayhem but I have no idea how hard they are to find, Most likely around but?

two other variations
303 US primer crimps

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Pete, both these .303 rounds are French re-worked .303 rounds. The 3 stabs on the US 15 headstamp signifies Incendiary and the 4 stabs signifies an “SPG” Tracer loading. They should both have no neck stab crimp on either.

The previous US15 VII photo with the 4 long primer stabs is unknown to me I have not seen that style or stab before.



Thanks for that. You are correct no neck crimps, However none of my other 15 or so 15 through 17dated have neck crimps ?

BUT I do have 2@ 17’s with what look to be French AP blackened bullet / smooth crimping cannelure. Photo of the rnds & primer crimps below

Now last & most important bit to me is: where is this French re-work information to be found?


I have a few scanned tables and documents I will find and put on here.


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Ta, looking forward to seeing it.

Me too - thanks Richard.

The French reworks were especially for French loaded AP and Tracer, using G&B projectiles, for Aircraft use ( Lewis and Darne)
They also may have replaced the Dupont powder with French Flake.
In 1939-40, this requirement ( crimping) had been forgotten, and when the British started re- allocating US made .303 to non combat use, because of primer jams, this was made clear to the US manufacturers…but the Brits still used the crimped 42 and 43 Production for Non-combat use
Training, Regulating Aircraft guns,
General Ground Use ( Home Guard, etc.) In GB.

Regards, Doc AV


Nice info Doc