ButlerFord45,
The other use for a primer wad is to soften the brisance of a rifle primer to that of a pistol primer to help keep the fouling of the sporting black powder grades (SWISS) soft.
Shooters using older rifles have been concerned over the use of pistol primers since they are somewhat shorter than rifle primers, which in some cases can "peen" the face of a breechblock since the pistol primer can get a running start, so to speak, in backing out of the case.
By using primer wads, which in some cases, depending on the shooter's experiments, may be 2 or more layers thick, the rifle primer can be used successfully with the SWISS grade of sporting b.p.
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