Originally Posted by
green granite
F5/34 design was powered by a 840hp Mercury and with this engine reached around 316mph
The Blackburn Roc also had the Boulton & Paul 4 gun turret with no forward facing guns; it was powered by a Bristol Perseus radial of 890hp and according to Wiki, was much slower than the Defiant with a cruise speed of 135mph (max 223 mph) compared to the Defiant's cruise of 175 mph (max 304 mph) with the 1030hp Merlin 111. In addition to the gun turret however, the Roc had bomb racks under the wings which could carry up to 4 x 250 lb bombs.
Rocs were built by Boulton and Paul at Pendeford, thus delaying Defiant production!
Wiki only mentions one 'kill' by a Roc, a Ju88 which was attacking a convoy off Ostende.
Another design with the Boulton and Paul turret was the Hawker Hotspur which additionally had one forward facing Vickers machine gun however this design did not get past the single prototype which flew in 1938, after the Defiant but slightly before the Roc..