buffer wad "pistoning"

[Jeff Mayhew]

I just loaded a bunch of 10 gauge black powder loads in RMC brass cases and noticed an interesting phenomenon. The buffer wads are heavy, lubricated wads of 3/8" to 1/2" thickness, and in a few cases I noticed that they were bottoming out but then retracting at least 1/8". In other words, they were tight enough to compress the air below them and then open up after the pressure from the tool was released. Like air-tight "pistons." The tool definitely bottoms out, hard, but then the wad backs out. You hit it again with the tool and it squishes down.

In the remaining loads I jammed a surgeon's scalpel down the center of the buffer wad to create an air path, and there were no problems. I checked the prior loads (hadn't yet glued in the over-shot card) and had to re-do 3-4 shells with this problem (if it's a problem).

Given all the concern about air gaps over black powder, I just thought I'd mention that. I don't know how important this is, but in the absence of more information I figure it's better to be "safe than sorry."

Perhaps I'm using a buffer wad that's too big for the RMC shells?