The primer

It is the smallest, most unimpressive component of the total system of weapon and ammunition – the primer. Nevertheless, it deserves our very special attention because nothing works without the primer.

It might have already happened to the one or the other in the hunting district or at the shooting range: The loudest noise in the world is a “click” when it actually should have been a “boom”. The reasons for such a more than annoying failure in the desired release of a shot are multifold. But nowadays it is very unlikely that it could have been the fault of a defective primer, or at least when it is of RWS manufacture. Since the Rheinisch-Westfälische Sprengstoff AG (RWS) did real pioneering work, which set standards worldwide and has been copied multifold, with the mercury-free Sinoxid primer that was patented in 1928.

The Sinoxid technology is based on the substances lead styphnate and tetracene. Lead styphnate is very storable and has excellent igniting effectiveness. The mixing in of tetracene again regulates the sensitiveness of the primer. With this, you obtain a priming compound, which distinguishes itself in high functional reliability and great safety in the handling. The shot is released with absolute reliability. In the period that followed, the progress in the primer technology was expedited as with no other company.

Thereby, in the development history of firearms the reliable ignition and release of the shot were certainly not a given, the opposite was the case. Since still at the end of the 17th century, even with muzzleloaders having the best flintlocks of their day, the ignition failure rate of the black powder loads was roughly 15 per cent, so that the shot release often compared with the lottery. Here you need to visualize that the shooters could not even focus on the target visually, because they were far too busy handling the ignition source and keeping an eye on the priming pan on the weapon. Anybody vividly can imagine how the hit results turned out under these circumstances.

In the development of the metal cartridge with integrated ignition source three ignition systems evolved, which distinguish themselves for the main part by the position of the anvil. The ignition composition needs a counter bearing, which is called anvil, in order to be ignited by the impact of the hammer pin.

  1. Boxer priming: With the original boxer priming the anvil was put into the case before the insertion of the primer and held by the pressed in primer.
  2. Berdan priming: The anvil is a permanent feature of the cartridge case.
  3. Anvil priming: A modification of the boxer primer and the currently most common system, where the anvil is part of the ignition system, which is completely installed in the case. The anvil primer consists of a cup with priming compound and a pressed in anvil (see illustration).

Cross section of an anvil primer 

  1. The lacquered sealing reliably protects against moisture 
  2. The ignition compound is an elaborated composition of primary explosive, sensitizer, oxidizer and reducer and ensures a sure and lasting burning of the powder bed
  3. Due to innovative coatings, the cup ensures protection even with extreme climatic conditions
  4. The shape and the perfect seat of the anvil ensure safe and fast ignition

For 115 years now, ammunition has been produced in the Middle Franconian city of Fürth and that much be mentioned beforehand: The industrial production and processing of primary explosives counts to the most hazardous operations in the chemical industry and thus requires high safety-related expense. The anvil primer consists of the four components cup, paper or foil cover with topcoat lacquer, ignition compound and anvil. The production of an RWS ignition composition takes place in twelve single working steps in ultramodern production facilities and comprises such as stamping, cup drawing, insertion of ignition compound, drying and pressing as well as insertion of the anvil.

The uninterrupted quality control already starts with the inspection of the delivered raw materials and is extended over the total production to the final product ready for delivery. The metal parts of the primer are examined in metallurgic tests for longitudinal strength, hardness, composition and grain structure. Further quality controls, in which the igniters are checked for dimensional stability and completeness with the most modern optoelectronic measuring instruments, are an integral component of the production sequence. Here everything spins around questions like: Has the ignition composition the correct quantity or are anvil, cover and lacquering in place? Finally, further physical and chemical test procedures with regard to sensitiveness and handling safety as well as ignition performance and geometry ensure that igniters with highest reliability are leaving Fürth.

The metal components in form of the cups and anvils originate from multistage production processes. They are finally nickel-plated and are convincing due to an accuracy of 1/100 millimetres absolute minimum tolerance. The ignition compositions in innumerable variants are tuned to the respective weapon/calibre/ammunition combination, so that a custom-made solution can be offered for every task. Nowadays, more than 200 different types of primers are being manufactured.

The latest Super Clean ignition technology (SINTOX) additionally disposes of a markedly temperature sensitivity and guarantees highest functional safety even under most extreme conditions: Between minus 60 and plus 71 degree C. Since in addition to that the lead content in this ignition composition was reduced to zero, there is no heavy metal pollution in the direct surroundings of the shooter. Another evidence for the technology leadership of RWS in this area is surely also the fact that the primers with Super Clean technology were the only ones worldwide that were certified by NATO.

„A steady change“

Dr. Ulrich Bley – with RWS for 18 years

PASSION asked Dr. Ulrich Bley, the head of the chemical laboratory of RUAG Ammotec what can be further improved with the primer and whether the electronic firing of the cartridge will soon replace the mechanical one.

The development of the modern primer seems to have already reached its climax with the heavy metal free RWS Super Clean technology. In your opinion, in which subareas is there still space for improvements?

Our goals are among others the steady improvement of quality in all subareas of the cartridge as well as the optimisation of the functioning. With the primer potentialities are conceivable in the limitation of the release barrier. The range from “No fire” to “All fire” – how it is so nicely said in new German – is being further restricted. This would provide the gun manufacturers new possibilities in the development of trigger systems. But on the other hand, you also have to be cautious here. Because of the existence of a great number of all different kinds of weapons and especially their state of preservation, it must be ensured that an RWS cartridge always functions. After all, ammunition has been manufactured in Fürth for 115 years and we have a reputation to lose.

Why have electronic trigger and ignition systems in your opinion until this day not become prevalent at least on the civil hunting and sports weapon market? Should electronics of today not allow favourable alternatives to the classical mechanical system?

The mechanical release has the advantage that functional safety is guaranteed under even adverse conditions. With electronic systems a battery must always be charged, the temperature range and the resistance against moisture are limited. Anyhow, as far as I know the electronic ignition has not become prevalent on the mass market as of yet and will also have no prospects in the foreseeable future. In my opinion, however, the combination of electronic stimulus with low energy and chemical release by ignition composition would be quite interesting. The cartridge would be preserved in its form of today and only the release mechanics respectively the firing pin would be exchanged, whereas energy sources other than batteries are imaginable here.

How does the future of the igniter look considering dwindling resources and other technological developments?

With the chemical substances the natural resource question is not the main problem since the requirements of ignition compositions are probably only within a range of below 500 tons a year worldwide. Considering these comparatively small quantities, a shortage on the part of chemistry is not to be expected. It might possibly look different with the metals for the cups. Here, alternatives have to be and are thought about. However, as the history of ammunition shows again and again, the development in case of cartridges is always evolutionary. Well, there is a steady change, which proceeds in small steps, as well as a coexistence of established and new technology. Thus muzzle-loading shooting with black powder is still very popular today. I see concrete future developments in the fulfilment of new requirements of legislation with regard to safety, used substances or limit values in indoor shooting ranges for example. Here, for example, we have already made significant progress with our Cineshot ammunition with heavy metal free ignition that was introduced in the year 2008, and which is very successful on the market.

Copyright Passion 8/2012

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