OK guys, here's a pictorial example of what I'm talking about.

Gun on the left is my Greener .577 conversion, with firing-pin holes measuring ~95 thou (2.4mm) in diameter. Gun on the right is a Birmingham BP-proved shotgun with firing-pin holes measuring ~150 thou (almost 4mm dia.). No way should anyone convert an action like that without bushing the strikers!

While I'm posting photos, your earlier request for pics of the Greener's breech with and without loaded cartridges was not forgotten, colorado.

Actually I cheated a bit here

The BP action with the over-size firing-pin holes is in fact a hammer-gun, so the strikers are bushed anyway, from the rear. Nevertheless, ruptured primers would be a strong possibility with full nitro loads IMHO.