Corrosive Mil-surplus ammo and Mercury

[madrad62]

what is the cut off year for corrosive .303?,i recently acquired a couple of cases of .303,mixed head stampes,year and manufacture. is there a list somewhere? help me,help me!

[Bruce_in_Oz]

ALL .303 ammo that uses the large (.250") copper-cupped primer is CORROSIVE and mercuric.

I treat ALL other "mil-spec" ammo with caution, be it WW2 US or Canadian made or from any other source. Remember that NOBODY was making "non-corrosive Mil-spec" ammo for ANYTHING apart from M-1 Carbine, until after WW2

If you find a stash of ".303"" ammo with no headstamp and three "stab"-crimps around the primer, it is probably WW2 Japanese production for (generally) IJN light and medium MGs. Not only is it old and fairly scarce, the primers are corrosive, but not mercuric.

Even today, "Government Issue" ammo in 7.62 x 39 (and 7.62 x 54R) is almost ALL corrosive, but definitely non-mercuric. Chrome-lining of barrels and hard-chroming of working parts was / is done for a good reason. The components that do cop a flogging from corrosion are the springs; especially "hidden" ones like extractor springs. Every time the action opens after firing, "fumes" containing minute traces of nasty stuff wash all over the working parts. You cannot "hard-chrome" springs; it just makes them brittle, and anyway, the flexing of the spring cracks the "protective" chrome coating.

In "public" or private use, there is no excuse for not cleaning firearms properly.

[madrad62]

thank you oz,some of this stuff is ww2. head stamps like [GB 50 7,RG 50 7,DA ^ IN C 44,W.R.A.4?,] AND OTHERS.all seem to have copper primers. I came across a#1mk3* and was curious how these funny looking rifles shoot. so I found some ammo on the cheap.real nice canvas bandos and chargers with a bunch of different manufactures of ammo[u,wra,gb,rg,da,hxp,]. im curious how it stacks up against a springfield 03.are there any more things to possibly attach to the barrel of an enfield?

[Merle]

1. No. Very few mercuric primers have been produced since 1950.

2. No. Mercuric priming has no harmful effect on the gun. It does spoil the fired cases for reloading.

3. No, there's no salt in a "corrosive primer". They contain potassium chlorate (not salt) that leaves a residue of potassium chloride (a salt) after it ignites.

4. No, you don't need the Windex. Water is all that's needed to dissolve the chloride residue and flush it out.

5. No, there's no need to flush the bore at the range - as long as you clean with water before nightfall.

6. No, your LGS owner is even more confused than you are.

+1, this pretty much nails it.

At the risk of starting a panic, I would mention that I BELIEVE it would be a good idea to wash out cases (fired with corrosive primers) before reloading.
I'm not sure how much residue is still inside the case, but better to be paranoid than find a rusted bore.

[Merle]

One quick way to ID priming compounds is to look at the primer cup.

If it is brass "coloured" it is ALMOST certainly "non-mercuric". If it is "copper" coloured, it is almost certainly Mercuric"

Why?

As regular users of Mil-Surp (Brit/Oz/Indian) .303 ammo find out, the brass, even if the ammo looks perfect, starts to develop cracks within weeks (or less) of firing.

This is because, on ignition, the mercury in the priming compound is "liberated" and suddenly sprayed at high pressure all over the front end of the case. Mercury has the annoying property of breaking the copper/zinc bond in the brass. This is "NOT a good thing".

That is why "mercuric" primers have "copper" cups; the mercury does not react with pure copper. If you look at early US made cartridges, like .44-40 and .45 Colt etc, a LOT of them have copper primers: these are soft and thus easy for early springs and mechanisms to ignite. They also probably contain Mercuric fulminate and interesting compounds that form REALLY corrosive salts upon ignition.

Our German cousins pretty much perfected "non-mercuric" (LEAD based) primers before WW1. The non-corrosive thing came a LOT later.

The biggest boost was the M-1 Carbine. Because these beasties had a "non-user-serviceable" gas system, they NEEDED "non-corrosive" ammo. Not just any old "non-corrosive" ammo, but "MIL-SPEC", first time, everytime sort of ammo.

Put simply, Mercury is the cause of brass embrittlement. The "salts" that are added to the brew in order to extend the "brissance (flash) of the primer are what causes the corrosion. My Canadian associates tell me that much of the "Great, White North" is so dry in the winter, that there is insufficient moisture in the air to combine with these salts to start corrosion. The onset of "Summer" somewhat changes that scenario.

With the advent of 7.62 NATO, it could never be anything BUT Non Mercuric, non-corrosive, apart from the bogus stuff produced in China, Bulgaria, Russia and several other "not-quite-NATO" countries over the years.

As for reloading Berdan primed brass: it is a lot more of a fiddle than processing Boxer cases, but, if Berdan is what you have in bulk, it CAN be done. The biggest problem these days is finding the primers.

RWS used to sell a wide range of brass-cupped Berdan primers:

RWS 6000 was THE primer for .303 Mil cases that used the 1/4" diameter, primer,

RWS 5608 was the "Mil-Spec" primer for virtually every major European military cartridge, not to mention Australian L2A2 7.62 NATO ammo.

RWS 5627 is the nickel-plated, slightly thinner-cupped version of the 5608 and works in a HUGE range of European Ex-Mil and sporting cartridges.

RWS also made a slightly bigger (only by a couple of thousandths) primer than the 6000; this was perfect for Russian 7.62 x 54 cases, as well as quite a few "odddball" English and European "express" cartridges.

Alcan in the US ONCE made/sold a wide range of Berdan primers, but probably not for a long time now.

I have also heard horror stories about bores "dissolving" with the next shot if not cleaned properly after mercuric primers.