Siegfried Gunter, Heinkel's chief designer, originally intended the He 177 to be equipped with three cockpit-controlled remote gun turrets, with two of them intended to come from the Junkers Ju 288 program, and only a single manned position in the tail. Compared with the manned turret, the idea of remotely controlled, turreted defensive armament traded technical complexity for reduction of size, weight, and drag. Furthermore, it held the advantage that the gunner could be installed in a protected position where he would have the best possible view, and where he would be less likely to be blinded by the flash from his own guns. Although work on remotely controlled aircraft defensive systems had reached a relatively advanced stage in Germany in the late 1930s, progress in this field was to prove insufficient to keep pace with the He 177. As a result the He 177 had to be modified to accommodate larger and heavier manned positions, such as the rear dorsal turret usually fitted to almost all examples of the Greif, armed with a single 13 mm MG 131 machine gun, this installation requiring that the fuselage receive structural strengthing in several locations.

He 177 nose with MG 81, 1943.
[Source: Bundesarchiv, Bild 101I-674-7766-25A/Keiner/CC-BY-SA]

Eventually, most of the later production aircraft did receive a single remote forward dorsal turret, the Fernbedienbare Drehlafette (translating as "remotely operated rotating gun-mount", and abbreviated "FDL") 131Z, armed with two MG 131 machine guns, located at a point on the fuselage directly above the wing root's leading edge, with its rotating hemispherical sighting station's dome located a short distance forward of the turret itself and slightly offset to starboard, just behind the forward cabin area.

A compact tail gun position was fitted from the beginning for rearward defense, and armed with a single MG 131 machine gun, but its streamlined glazing, which demanded a prone gunner accommodation, severely restricted the gunner's comfort, so a revised tail gun position with a bulged upper glazing design which permitted the gunner to sit with their upper body upright, requiring a reduction of the lower end of the rudder surface for clearance, was fitted to the He 177 A-3 and later models, the initial being often replaced with a 20 mm MG 151 cannon, or in a very few instances a semi-experimental twin MG 131Z mount, with the twinned 13 mm calibre guns mounted one above the other at the rear of the standard bulged upper glazing emplacement.

Good view of the He 177 tail gun position.
[Source: Unknown]

Usually, a single 7.92 mm MG 81 machine gun in a flexible mount was mounted in the upper starboard side of the cockpit nose glazing, for defense from a direct frontal fighter attack.

The undernose, inverted-casemate Bola gondola (a common ventral armament fitment concept for many German bombers), which was the full width of the fuselage where it emerged from under the nose, and centered under the forward cabin, usually had a flexibly mounted 20 mm MG FF cannon at the front end, and a flexibly mounted MG 81 machine gun in the rear for the initial A-1 version. A MG 151 cannon would replace the forward MG FF cannon in later production models, with a single MG 131 replacing the MG 81 for rearwards ventral defense.

Gunner getting into the He 177 tail gun position.
[Source: Unknown]

In addition to carrying a variety of bombs, torpedoes, and guided weapons the He 177 was tested with a number of unorthodox offensive armaments. The first of these experimental weapon schemes known to have been tested were the twelve examples of the He 177 A-1/U2 Zerstörer variant, which was armed with a pair of limited-traverse 30 mm MK 101 cannons in the extreme front of a dramatically enlarged Bola ventral gondola, and intended for ground attack, train busting, and possibly long-range anti-ship raids. Later, when assigned to flak-suppression sorties in the area of Stalingrad during the winter of 1942, Luftwaffe forward maintenance units modified a small number of He 177s, fitting a 50 mm Bordkanone BK 5 cannon within the aircraft's undernose Bola gondola, with the long barrel protruding well forward, beyond the glazed "fishbowl" nose. This variant was unofficially dubbed the Stalingradtyp. Although a small number of He 177 A-3/R5 models were to be built from scratch, with the l arger PaK-40-based, autoloading 75 mm Bordkanone BK 7,5 ventral cannon, structural problems caused by the weapon's recoil meant that the Stalingradtyp did not see combat use outside of the original, BK 5-armed improvised handful.

Five He 177 A-5s were experimentally equipped in January 1944 with batteries of thirty-three obliquely mounted 21 cm (8-1/4 in) calibre rocket mortar tubes, likely derived from components of the Nebelwerfer infantry barrage rocket system, to create the Grosszerstörer ("Big Destroyer") flying battleship, meant to break up and destroy the tight combat box defensive formations used by USAAF daylight bombers over Germany. The bomb bays and fuselage-housed auxiliary fuel tanks were removed on these aircraft in order to provide space for the spin-stabilized 21 cm (8 in) rockets and their firing tubes. The tubes were inclined to fire upward at an angle of 60° to the horizontal axis of the aircraft and slightly to starboard. The tubes could be fired individually, sim ultaneously, or in two salvoes of fifteen and eighteen. Tests with fixed balloon targets showed the potential of this system, and limited operational trials against US Eighth Air Force bomber streams were authorized. The aircraft were operated by Erprobungskommando 25, flying out of the Baltic coastal Erprobungstelle facility at Tarnewitz. The intended mode of operation called for the He 177s to follow the enemy bomber formations, passing below (as with a Schr├Ąge Musik cannon fitment) and to port of the target, maintaining a difference of altitude of 2,000 m (6,560 ft) beneath the targets at the time of the attack from below. A few trial daylight operations were flown but no contact was made with Allied bomber formations, and as the escort fighters were becoming ever more numerous - in the manner of air superiority-purpose "fighter sweeps" well ahead of the massed USAAF bomber formations, starting in early 1944 - the entire scheme was abandoned.

Experimental defensive weapons fitments were also tried on small numbers of 177s set aside for such trials, mostly at the Erprobungstellen test detachment fields. One such fitment was to an He 177A-1, s/n 15155 with Stammkennzeichen GI+BP, which was the first-ever example of an He 177 to be fitted with an experimental, remote control twin-gun "chin turret" at the front of its Bola undernose gondola. The type of guns to be fitted was not recorded, but the date of which GI+BP was written off from a mishap in May, 1943 would place the fitment of its experimental "chin turret" simultaneously with the lead-up to the May 1943 service introduction of the "gunship" USAAF Flying Fortress, the YB-40, which pioneered the same type of forward defensive armament on the best known American heavy bomber to attack Nazi Germany. Similarly, the much-anticipated Hecklafette HL 131V "quadmount" manned tail turret, armed with a quartet of MG 131 machine guns, was first tried in the late spring of 1943 on a pair of A-3 examples set aside as the V32 and V33 prototypes, but never made it to production status.