Minnie ball

[Peter r]

Why does .69 rifled smooth bore have a wooden plug below Minnie ball ?

 

[Llewellyn]

Why does .69 rifled smooth bore have a wooden plug below Minnie ball ?

Early Minie balls had a wooden or ceramic plug which was driven into the base of the bullet by expanding gas, to spread the skirt which would then engage tightly with the rifling.
It was quickly discovered that a simple hollow base would expand the skirt on firing, without the need for a plug.

What is a rifled smooth bore ? Ain't it one or the other ?

 

[Peter r]

A smooth bore that has been modified to have a twist through the barrel , thanks for that clarity