Sherman V Firefly 

Type: Medium tank

Nationality: Great Britain

The most successful attempt to upgun the Sherman was British. They put in the turret their excellent 17-pounder gun. The alterations inside were drastic (counterweights, lengthening of the rear compartment to absorb the recoil, ...). Although it had taken some weight with the new weapon, it was the only model of Sherman that could face a Panther without too much of an handicap.
Identification: The very long gun with a muzzle brake and the overhang behind the turret allow to recognize a Sherman Firefly, whatever the hull on which it is mounted (most of them were on Sherman V M4A4).
Built by N/A
Other designation(s): Firefly (Sherman)
Based on: Sherman

A British 17-pounder gun mounted on the hull of a Sherman gives the excellent Firefly. Note the compartment behind the turret. Indispensable to compensate for the extra room needed by the big gun.