Firing pin hole size -76' Topper

[444Dan]

On a previous post I asked the question about firing pin hole sizes on the various frames SB1/SB2 and the older frames out of the concern with primers flowing into the hole. I measured the hole size on my 76' 058 Topper 16 ga and it was 0.072/0.073".  Out of curiosity I happened to have a fired .223 casing from my Mini 14 close by and measured the primer indention and found that it was at least as large as the Topper and probably a couple thousands larger.   Based on this I don't think I would need to worry about primer issues if I were to fit an extra barrel in 357/44 mag or even the 30-30.  Obviously, higher pressure cartridges would be out of the question due to the cast iron construction but I have no interest in adding those to this frame.     Am I missing anything else?  BTW- love this board, great info from all you seasoned handi users.   Thanks

[trotterlg]

You are probably over worrying the problem, but here are a couple of thoughts.  First just measure the fireing pin in your Mini 14, measureing the dent is no way to do it.  Just as important as the size is how much clearance there is from the hole in the breach to the pin, too much causes "blanking" with any size pin, this where the metal flows into the gap and is basically cookie cuttered out of the primer making a nice hole.  Excess headspace can also cause primer piercing as well as a host of other things including the shape of the tip of the pin.  If I were to do a low pressure barrel on the frame I would just mount it up and shoot one with it tied to a tree and see what you get.  Then worry about fixing what is probably a non-existing problem.  Larry