Primers: An Important Factor in Precision Reloading

) Lee Hand Press Kit is a modern version of the old “tong tool.” This kit includes dies, case lube, powder dipper, etc., for a little over $65.

Lee Hand Press Kit is a modern version of the old “tong tool.” This kit includes dies, case lube, powder dipper, etc., for a little over $65.

Centerfire ammunition soon pushed all the other non-reloadable types out of the market because it was reloadable. Rimfires were gradually reduced to those types that were small and efficient in calibers that would not lend themselves to reloading.

The military had great influence in ammunition development stipulating that any ammunition developed for a military small arm had to be reloadable. Spent cases were collected and returned to a government arsenal for reloading during peacetime. Professional hunters in the American west needed cartridges they could reload themselves with simple tools. It was this type of equipment that first appeared in the 1870′s.

Early priming mixtures used fulminate of mercury or potassium chlorate, eventually, a combination of both. These fulfilled most of the criteria for good ignition — speed, reliability, uniformity and cleanliness, with the possible exception of cleanliness. While the chlorate-based primers did not leave an appreciable residue, they did leave a highly corrosive deposit — potassium chloride — that would eat away a percussion nipple or the web of a cartridge unless neutralized by cleaning with water that removed the salt deposit. The mercury-based compounds were both clean and non-corrosive. Their drawback came when used in combination with brass or copper primer cups and brass or gilding-metal cartridge cases.

When fired, the mercury would amalgamate with the copper or brass, making it extremely brittle. The heavy fouling of blackpowder had a mitigating effect on mercury contamination, keeping it in the fouling allowing removal. With smokeless powder, reloading and firing such a contaminated cartridge case can lead to a case-head rupture. In a high pressure loading this can wreck a gun and possibly your face. Mercuric priming was gone from commercial ammunition by about 1945, but mercuric primers made prior to this time were used by commercial reloaders after that and some of them may still be on shelves somewhere.

Because fulminate of mercury contains free, liquid mercury, this mercury will actually migrate through the priming mixture and into the metal of the primer cup or cartridge head after a certain number of years. Ammunition primed with mercuric mixtures made in the early 1930′s will probably not fire today while ammunition loaded with chlorate priming made during the Civil War is often still viable, so long as neither the powder or priming compound has been exposed to moisture. Thus a fifth criterion should be added to a successful ignition system — long life.

From 1928 through 1935 American manufacturers worked to perfect a priming mixture akin to the one developed in Germany that was non-corrosive and did not contain mercury. The basis of such priming is in compounds of lead, barium and antimony.

>Early non-corrosive, non-mercuric primers did not work very well, giving uneven ignition. Priming material often fell out of the rim in rimfire cartridges as the binding material — a vegetable-based glue — deteriorated.