H B, the muzzle.
A o, the cascabel, or pomiglion.
A C, the breech.
C D, the vent-field.
F I, the chace-girdle.
r s, the base-ring and ogee.
t, the vent-astragal and fillets.
p q, the first reinforce-ring and ogee.
v w, the second reinforce-ring and ogee.
x, the chace-astragal and fillets.