RWS 4 mm 250 caps are long primers with a standard initiating charge, designed for rifles and black-rifles.
The caps are responsible for igniting the powder charge. The size of the percussion caps and the type of primers (standard charge or increased charge) should be adapted to the size of the chimneys of the black-powered weapon.
The1055 caps have a high ferrule, so they do not fit black-rifle revolvers.
