Lead ?

[TexasMac]

Here’re the Miroku Mfg. Browning BPCR chamber casts and some specs. Miroku cut the chambers per specs provided by Browning.

The .45-90 has a 12.75 degree transition step from chamber to bore. It has a 0.150” freebore and a 1.5 degree leade angle. As noted by the photo, the chambers are identical, which should not be a surprise since Miroku cut both chambers.



The .45-70 has a 12.75 degree transition step from chamber to bore, which continues to the top of the lands, resulting in a leade angle of 12.75 degrees. There’s no freebore.



The .40-65 also has a 12.75 degree transition step from chamber to bore. It has 0.0100” of freebore and a leade angle of 1.5 degrees.



Wayne