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.