Introduced 1875 and discontinued 1887, when the word 'CHOKE' replaced it.

It was a warning not to use ball ammunition in choked guns. After 1887 ammunition manufacturers loaded ball smaller than a full choke in size so ball could be fired from a choked barrel without damage.

I would check before using ball on the size and make sure that the ammo you intend to use does indeed fit down the entire barrel length, including the choked section before using it live.

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