A Needham Conversion hammer is a standard M1863 hammer with modifications.
The hammer is cut in order to enable a wedge to be pinned to the hammer to strike the firing pin.
It should be noted every Needham Conversion uses a M1863 style hammer whether or not the rest of it is a M1861.
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On the left is a standard Springfield M1863 hammer. On the right is a M1863 Needham Converison hammer.
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