I just purchased a couple of Squadron/Signal books, Junkers Ju 88 in action Part 1, and Part 2 - this is the information presented within.
Ju 88A-4 machinegun/cannon armament
Pilots gun, starboard windscreen: MG 81, often replaced with an older MG 15, because the ammo box on the MG 81 obscured the pilots view. Some had the MG 131 instead
Forward flexible gun, lower nose panel: MG 15, MG 81, MG 131 or very rarely, a twin MG 81Z
Rear upper guns: two MG 81 installation, or single MG 131
Ventral gun, gondola: MG 15(Bola 39), twin MG 81Z(Bola 81Z), or MG 131(Bola 39D VE)
Side mounts, "donuts": On each side are small circular holes in the canopy where a single MG 15 or MG 81 could be fitted. Very rarely used, but capability seems to be present on all aircraft
Frontal cannon: Änderungsmaterial(alteration material) conversion kits were used to fit a single MG FF in the starboard side of the nose, replacing the flat glass panel with a concave panel reinforced to hold the cannon. The Lotfe bombsight was removed and the optical glass on the ventral gondola faired or painted over. The gun was fed by 120rnd drums which could be reloaded by the bombadier.
The success and popularity of this kit led to factory modifications to install the cannon inside the ventral gondola. On late production Ju 88A-4, the front of the gondola was flattened to allow for mounting of the MG FF. Either the cannon or Lotfe bombsight was fitted, but not both at once.
External and internal ordinance
Bomb-bay loads: The fuselage bomb-bay loads(as recommended by the Ju 88A-4 handbook) included several Rüstzustand(Equipment States):
Equipment State A - Up to ten 50kg(110lb) bombs in both the forward and rear bays(20 total)
Equipment State B - Up to ten 50kg bombs in the rear bay and one 1,220 liter(322 gallon) fuel tank in the forward bay.(This was the most common configuration).
Equipment State C - One 322 gallon fuel tank in the forward bay and one 680 liter(179.5 gallon) fuel tank in the rear bay.
External loads: The inner ETC racks could carry up to 1000kg(the lettering "1000kg" can be seen printed on them in one photo) bombs, or 900 liter(237.6 gallon) drop tanks, and the outer ETC racks up to 500kg bombs.
Torpedoes
The Ju 88A-4/Torp was created by the application of a modification kit to a standard Ju 88A-4. It consisted of removing the slatted divebrakes and ETC racks, and installing two PVC torpedo racks under the wing roots. This enabled the Ju 88A-4/Torp to carry two 1,686lb LT F5b or similar torpedos. All other armament and equipment remained identical to the Ju 88A-4.
Zerstörer versions
Turns out the Ju 88C-4 was based on the earlier(cronologically) Ju 88A-5, not the more powerful A-4. The C-6 was based on the A-4. The divebrakes, bombsight and pilots gun were removed, and a solid nose cap fitted. Armament was three MG 17 and a single MG FF(120rnd drums) or MG 151(350rnds) in the nose, and two MG FF(120 rnd drums) in the ventral gondola.
Ju 88S-1
A streamlined and lightened Ju 88A-4. The ventral gondola was removed, only essential armour was kept, only a single MG 131 rear upper with 250rnds, and only two ETC wing racks stressed for 1000kg bombs. The engines were 1730HP BMW 801G-2 radials with GM 1 boost, the 900 litres of liquid being held in three tanks in the rear bomb-bay. At normal injection rate there was 45 minutes supply, at emergency rate, 27 minutes. With GM 1 boost the top speed went from 340mph to 379mph, and ceiling from 34,000ft to 38,000ft.
Tank busters
The most common version seems to have been the Ju 88P-2, a Ju 88A-4 with solid nose cap, and two BK 3.7 in a large ventral gondola. Defensive armament was two MG 81 rear upper, and a twin MG 81Z in the rear of the cannon gondola, plus the pilots windscreen MG 81. The P-2 was used against both ground targets and tanks, and briefly against USAAF heavy bombers. The heavy cannon severely reduced performance and manoueverability, top speed being about 244mph.
[This message has been edited by juzz (edited 11-20-2000).]