The 56-50 Spencer (Taylor's) was built to C.I.P. specifications for operation in the Taylor Arms 56-50 Spencer. Rim diameter is .629" to .632", which may be too small to eject properly in some originals. Rim thickness is .057" to .061". Thickness of wall at mouth is .0125" average. Case mouth may need to be annealed if not sealing properly with low pressure loads. Maximum bullet seating depth is .375".