Messerschmitt Bf 109E showing the MG 17 machine guns in the cowling.
[Source: Unknown]

Bf 109E-1
The E-1 production version kept two 7.92 mm MG 17s above the engine and two more in the wings. Later, many were modified to the E-3 armament standard. The E-1B was a small batch of E-1s that became the first operational Bf 109 fighter bomber, or Jagdbomber (usually abbreviated to Jabo). These were fitted with either an ETC 500 bomb rack, carrying one 250 kg (550 lb) bomb, or four 50 kg (110 lb) bombs. The E-1 was also fitted with the Reflexvisier "Revi" gunsight. Communications equipment was the FuG 7 Funkgerät 7 (radio set) short-range radio apparatus, effective to ranges of 48–56 km (30–35 mi). A total of 1,183 E-1 were built, 110 of them were E-1/B.

   – E-1/B (Fighter-bomber version of E-1, usually with DB 601Aa)

Bf 109E-2
Only very limited numbers of the E-2 variant were built, for which the V20 prototype served as basis. It was armed with two wing mounted, and one engine mounted Motorkanone MG FF cannon, which gave considerable trouble in service, as well as two synchronized MG 17s cowl machine guns. In August 1940, II./JG 27 was operating this type.

Messerschmitt Bf 109E-2 (V20), coded CE+BM, WkNr 1953.
[Source: Unknown]

Bf 109E-4
The E-3 was replaced by the E-4 (with many airframes being upgraded to E-4 standards starting at the beginning of the Battle of Britain), which was different in some small details, most notably by using the modified 20 mm MG-FF/M wing cannon and having improved head armour for the pilot. With the MG FF/M, it was possible to fire a new and improved type of explosive shell, called Minengeschoß (or 'mine-shell'), which was made using drawn steel (the same way brass cartridges are made) instead of being cast as was the usual practice. This resulted in a shell with a thin but strong wall, which had a larger cavity in which to pack a much larger explosive charge than was otherwise possible. The new shell required modifications to the MG FF's mechanism due to the different recoil characteristics, hence the MG FF/M designation.

The cockpit canopy was also revised to an easier-to-produce, "squared-off" design, which also helped improve the pilot's field of view. This canopy, which was also retrofitted to many E-1s and E-3s, was largely unchanged until the introduction of a welded, heavy-framed canopy on the G series in the autumn of 1942. The E-4 would be the basis for all further Bf 109E developments. Some E-4 and later models received a further improved 1,175 PS (1,159 hp, 864 kW) DB601N high-altitude engine; known as the E-4/N; owing to priority being given to equipping Bf 110s with this engine, one fighter gruppe was converted to this version, starting in July 1940. The E-4 was also available as a fighter-bomber with equipment very similar to the previous E-1/B. It was known as E-4/B (DB 601Aa engine) and E-4/BN (DB 601N engine). A total of 561 of all E-4 versions were built, including 496 E-4s built as such: 250 E-4, 211 E-4/B, 15 E-4/N and 20 E-4/BN.

• E-4 (Armour and structural improvements, change of MG FF cannons to
   MG FF/M. "Square" canopy)
   – E-4/B (Fighter-bomber version of E-4, 1 × 250 kg bomb, usually with
      DB 601Aa)
   – E-4 trop (Version of E-4 modified to serve in tropical regions)
   – E-4/N (E-4 with DB601N engine)
   – E-4/BN (Fighter-bomber version of E-4/N, 1 × 250 kg/550 lb bomb)

Bf 109E-5/E-6
The E-5 and E-6 were both reconnaissance variants with a camera installation behind the cockpit. The E-5 was a reconnaissance variant of the E-3, the E-6 was a reconnaissance variant of the E-4/N. Both retained 2 x 7.92mm MG 17 machine guns for armament. Twenty-nine E-5s were built and nine E-6s were ordered.

Bf 109E-7
The E-7 was the next major production variant, entering service and seeing combat at the end of August 1940. One of the limitations of the earlier Bf 109Es was their short range of 660 km (410 mi) and limited endurance, as the design was originally conceived as a short-range interceptor. The E-7 rectified this problem as it was the first Bf 109 subtype to be able to carry a drop tank, usually the standardized Luftwaffe 300 L (80 US gal) capacity unit mounted on a centre-line rack under the fuselage, which increased its range to 1,325 km (820 mi). Alternatively, a bomb could be fitted and the E-7 could be used as a Jabo fighter-bomber. Previous Emil subtypes were progressively retrofitted with the necessary fittings for carrying a drop tank from October 1940. Early E-7s were fitted with the 1,100 PS DB 601A or 1,175 PS DB 601Aa engine, while late-production ones received 1,175 PS DB 601N engines with improved altitude performance – the latter was designated as E-7/N. A total of 438 E-7s of all variants were built.

Sub-Variants:
– E-7/N - Similar to E-4/N but with optional 300 L tank
– E-7/NZ - E-7/N with additional GM-1 nitrous oxide injection system
                 (also known as E-7/Z)
– E-7/U2 - Ground attack variant of E-7 with additional armour

Bf 109E-8
The E-8 was a long range version of a Bf 109E-1 using the drop tank fittings of the E-7. The armament remained the same as the E-1, 4 x 7.92mm MG 17 machine guns.

Bf 109E-9
The E-9 was a reconnaisance version of the E-7N. Fitted with a drop tank, camera equipment and reducing the armament to 2 x 7.92mm MG 17 machine guns.