Agree that the gun in the picture doesn’t appear to be a Breda, but neather a Scotti. The 20 mm Isotta Fraschini Scotti AA gun was 1,54 meters in lenght. If you compare, in your picture, the gun lenght and the man’s height, you can easily realize that the gun lenght couldn’t be one meter and a half…
For this reason i go for the 20 mm Oerlikon AA gun, that had a lenght of 2,21 meters (87 in).
The picture (below-left) was shot on the HMS Hermione and shows, exactly, an Oerlikon AA gun. The HMS Hermione was completed in 1941 and sank, in Mediterranean Sea, by the German U-Boot U-205 on June 15th, 1942.
As far as i remember the first Oerlikon built in USA was test-fired on June 8th, 1941 and 379 had been delivered by December 7th, 1941. But i am told that production and deliver, in UK, started before.
I found the second picture with the following caption This 20 mm Oerlikon anti-aircraft gun is manned by Frank Kalar, of Riverside (CA), crew member of an US destroyer escort, 1943.
I think that the gun in the picture you posted, spruso, should be an Oerlikon.