TECHNIQUE
The sectional figures below show the conventional techniques used to load cartridges. You will understand how PURNAT products revolutionise the transfer of energy within a cartridge.
FIBRE WADDING - PLASTIC WAD
The diagram shows the conventional loading of a cartridge with fibre wadding. In this case, we have a plastic wad placed on the powder. It is surmounted by a fibre wadding and shot.
CUP WAD
The diagram shows a cup wad that is placed over the powder and contains the shot in its recess
The part of the plastic wad or cup wad which contains the powder
swells at the moment of the explosion, which is what creates the seal.
This seal is obtained by the stretching of the material.
It is the elasticity of the plastic that makes this possible.
CARDBOARD OVER POWDER
In this diagram, the element placed on the powder is a cardboard wad, which is made of cardboard treated to be strong enough to withstand the explosion. It is an alternative to plastic, but it reduces the effectiveness of the ammunition. In effect, this cardboard disc is cut to fit into the casing, and the case also has a clearance so that it can be inserted into the barrel chamber without force. In the same way, the thickness of the casing also has a tolerance. The addition of all these tolerances together stops this cardboard disc from creating an optimal seal. Compared to plastic products, it is difficult to obtain the same speeds for the same pressure. This an even greater problem when ammunition is loaded with steel shot.
FIBRE WADDING
PURNAT WAD
The diagram shows a PURNAT wad placed on the powder.
It is surmounted by a fibre wadding and lead. The PURNAT wad, with its diameter smaller than the inner diameter of the case, ensures optimal assembly.
TECHNOLOGICAL INNOVATION
In this diagram, you can see the wad flattening out like cardboard on the powder. Unlike the cardboard on the powder, this flattening generates an increase in its diameter which becomes greater than that of the case; on its circumference, the wad pushes against the case, deforms it, and places it under pressure against the barrel chamber. In this position, the wad is compressed on its two faces by the gases that press it against the fibre wadding, and it is compressed by the case in the barrel chamber. In fact, the wad is not stretched but is compressed on itself, and the seal is obtained by compression and not by stretching.
The entire assembly and cartridge clearance in the barrel chambers is more than compensated for, resulting in optimum sealing. Even when the petals of the wad give way, they are stacked in such a way as to maintain the seal.
The efficiency of Purnat wads allows the best speed/pressure ratios to be achieved. The Purnat wad outperforms plastic products at low temperatures, and plastic also has its limits. Purnat successfully combines ballistic and environmental performance.
