I'm in need of some help identifying this.

Approx sizes are
Length - 139.83mm
Body dia - 25.03mm
Head/base dia - 28.79mm
Brass nose - 32.52mm
Brass base 12.43
It's body is steel (magnetic) with a brass nose piece and base. There is a small hole where a percussion cap would go but it's too small and only about 1-2mm deep but other than that no other markings. Not sure if it's mock up of something, any ideas?
Regards
John P

Approx sizes are
Length - 139.83mm
Body dia - 25.03mm
Head/base dia - 28.79mm
Brass nose - 32.52mm
Brass base 12.43
It's body is steel (magnetic) with a brass nose piece and base. There is a small hole where a percussion cap would go but it's too small and only about 1-2mm deep but other than that no other markings. Not sure if it's mock up of something, any ideas?
Regards
John P