During the dark days of 43, where the Luftwaffe were decimating the B-17F's with head on attacks, several aircraft received a field mod to remedy this German tactic.
Quite a few aircraft were modified with a twin 50cal, the bomb sight was removed and am armored plate was installed to protect the gunner.
It is said that these aircraft with this configuration flew wing on the lead ship to combat the head on stuff.
Ground personnel of the 303rd Bomb Group prepare to load bombs into a B-17 Flying Fortress nicknamed Wallaroo. Passed as censored then marked Confidential 27 Aug 1943. Note the censored area

B-17F 41-24527 324th Bomb Squadron 91st Bomb Group. CAPT Robert K. Morgan pilot of the Memphis Belle flew at least one mission in the aircraft.

1LT John T. Hardin crew 322nd Bomb Sq 91st BG with B-17F 41-24453 The Bearded Beauty-Mizpah coded LG-O.

LT John T. Hardin of the 322nd Bomb Sq 91st BG in the cockpit of B-17F 41-24453 Mizpah - The Bearded Beauty coded LG-O 27 February 1943.

B-17F Gremlin Trainer of the 305th BG.

2 June 1943 CAPT Charles R. Giauque%20 crew of the 323rd Bomb Sq 91st BG with B-17F 41-24524 The Eagles Wrath coded OR-O.

Lt. Reeder And Crew Of The 359Th Bomb Squadron 303Rd Bomb Group Beside The Boeing B-17 The Duchess. England 17 July 1943.

Lt. Stallings And Crew Of The 360Th Bomb Squadron 303Rd Bomb Group Based In England Pose In Front Of A Boeing B-17 Thumper Again. 20 July 1943.

B-17F Temptation probably assigned to the 95th BG.

B-17F 41-24547 Vertigo coded OR-P of the 323rd Bomb Sq 91st BG Bassingbourn.

B-17F 42-29816 The Eager Beaver coded LL-K of the 401st Bomb Sq 91st BG.

A tankman of the 55th Royal Armoured Corps in the nose gun position of a B-17 Flying Fortress nicknamed "Martha the II" of the 381st Bomb Group during a visit to Ridgewell, 1 September 1943.'British Tank Men Visit "Flying Corps". Men of the 55th Royal Armour Corps, many of whom have fought in Libya with the 8th Army, were invited to an American aerodrome


B-17F-303rd Bomb Group.

B-17F serial 42-29793 Sheila B. Cummin coded LL-F of the 401st Bomb Squadron 91st Bomb Group.

Also in 43 the Americans were concerned about German attacks from above with bombs.
"As part of a scheme intended to attack enemy aircraft flying above B17 bomber formations, a trial was carried out in mid-1943 of a four tube upward firing rocket installation. The four launcher tubes were around 12 feet long and angle 4 degrees forward protruding through the mid-upper gun turret modified to remove the perspex and guns.
The photo shows them in the radio compartment??
The trial aircraft was flown from Bovingdon to Pembrey and trial firing carried out successfully over Cardingan Bay. It is reported that the tubes could be reloaded in flight with the 3 inch rockets armed with a light HE warhead and time fuze.

The codename 'Sunflower' was used as a cover for the installation and 'Sunflower Seeds' for the rockets."