Quote:
Originally Posted by rwsmith
It seems I saw a video that Speer made that showed that a primer normally backs out upon firing, then as the main recoil drives the casing back, the primer is reseated.
Does anybody know anything about this? I suppose it would be easy to check out because the primer seated deep would be flush with the surface after being reseated.
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You recall correctly. That's exactly what happens:
1. It works just that way with normal power loadings.
2. With very high power/pressure loads we've learned to look for indicators like the machining marks from recoil shield imprinted on the primer and even cratered primers where the primer actually flows back into the firing pin bushing hole.
3. Low power/pressure loads can leave primers high.
4. To test this phenomenon, fire a primer in an empty case, it will bind up the cyl every time. To make blanks or wax bullet loads the flash hole in the primer pocket must be drilled oversize to prevent binding. The primer has enough pressure to drive out the primer like normal, but there's no opposite back pressure from a powder charge to drive the case back to re-seat the primer.
5. A light weight gun exacerbates the issue because the whole gun recoils more which mitigates the back pressure that re-seats the primer. Similar to the way too lightly holding a semi auto causes the slide to malfunction by not fully ejecting the empty case. There's not enough resistance to the recoil for the slide spring to operate correctly.