Primers - physics and chemistry ?'s
 

Ok .... anyone got answers here ....... are modern primers still based on lead Styphnate? If not - are there any compounds now in use which are lead free, and if so - what is the chemistry.??

I imagine we still require a compound with adequate brissance.

That begs another question ... which is - is there any published figure or figures, with regard to the impact energy required to initiate primer compound? Obviously primer thickness a factor but - any figure, in Joules, ft lbs .... kg's per cm^2 ... etc?

Just curiosity ..... to see what input we can get here.

Most primers still use lead styphnate, the new non-toxic primers such as those used in Winclean ammo do not. As far as I know, the non-toxic primers are not available to the reloader and may have a shorter shelf life.

Sorry, I don't have the detail information at hand here before coffee, but the main ingredient of most lead free primers has been published. I have seen ignition data in the past, too. It may not be in scientific units, it used to be given as the height a weight had to be dropped from to fire no, half, and all the primers tested. But you can convert when the numbers come along.

Lead free primers are slightly available. PMC "Green" primers are supposed to be getting available for sale and I have seen an advertisement for a Russian import primer. They *claim* to have reached normal shelf life and sensitivity. A test on the Russian stuff showed good uniformity and they attracted some interest in BPCR... but it seemed temporary.

Don't know about the primary reaction, but I understand manufacturers use a greater or lesser amount of various chemicals, including magnesium, to adjust the strength/length of the primer flame ("brisance"). (Per John Barsness) I suspect this difference in brisance is the basis for the "cooler" or "hotter" primers.

Jaywalker

Thx for replies ...

Jay ... as I always understood it, ''brissance'' .... or''brisance'' ... danged if I remember the correct spl ...... is surely the sensitivity .... how hard it needs hit if you like. Not so much length of flame produced.

Tri ammonium iodate, or ammonium tri nitride .. is brissant to point of absurdity when dry --- viz, can be set off by a fly landing on it! That is what I think of as brissance, also a term a guy I used to know in EOD used. Picrate too is IIRC way more brissant than std priming compounds.

Mind you - open to correction .. and must check it out.

I'm not positive about this, Chris, but I always thought brisance was the destructive effect an explosion carried with it. For extreme examples, a FAB has a tremendously higher brisance than a flash-bang even though it might take the same amount of percussive force to set them off.

[Heading to Google to see if anything can be found on it ...]
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I'm back. Found this at ordnance.org: So my FAB example wasn't quite fitting for the definition, but a block of C4 vs a flash-bang would be.

I once read that the old test for brisance was to put a small sample of the explosive of interest in the middle of a weighed pan of sand and detonate it. Brisance was recorded as the amount of sand blown out of the pan.

Not a characteristic you want in a primer.

Mal - yeah that sounds more familiar, thx ... I am I think simply confusing sensitivity with brisance. It's the aging brain syndrome and I have little excuse for forgetting .... except it was 1985 when I got my shotfirer's certification .. at which point I remembered this stuff.!

Brisance then really is an energy factor with speed factored in. ''VOD'' is relevant here ... ''velocity of detonation''. PETN (polyerythrytoltetranitrate) is about IIRC a VOD of some 8 km/sec ... and thus a component of blasting caps due to its brisance .... which will initiate thru that disruptive shock a detonation in - say - blasting gelatin.... itself having IIRC a VOD of around 5 km/sec.

Interesting and important also to discriminate between true detonation ... as happens with last examples .. and simple deflagration .. which we see in gun powders. Both loosely cause ''explosion'' .... which is rapid gas expansion, usually beyond speed of sound but .. generally the shock wave front of highly brisant materials that detonate will always be way more extreme in damage potential.

Brisance googles well.
One good read on primers is Chapter VI in George E. Frost's excellent Ammunition Making , a National Rifle Association of America publication.
Cheers from Darkest California,
Ross