Ok first let me say I am not claiming to be a gun expert, so if I am wrong with anything I say in this post just let me know. Ok lets start (sorry if this is overly simple like I said I am not a gun expert)
TA-152H guns
MK 108 cannon:
30mm
ROF 650 rds/min
Muzzle velocity 1770 feet/sec
Ammunition
The cannon used specially-developed 30x90RB mm ammunition—30 mm calibre, 90 mm case length, rebated/reduced rim. Unlike most other weapon rounds, which used traditional brass for the case, the MK 108's ammunition used steel cases. Several types of ammunition were developed, including practice, armour-piercing, high-explosive and incendiary. In operation, however, two major ammunition types were used: Minengeschoß ('mine-shell') high-explosive and incendiary. The Minengeschoß was made by drawn steel (the same way brass cartridges are made) instead of being cast as was the usual practice for cannon shells. This resulted in a shell with a thin but strong wall, which hence had a much larger cavity in which to pack a much larger explosive or incendiary charge than was otherwise possible. The incendiary rounds were also often fitted with a hydrostatic fuse, which detonated when it came in contact with liquid. This was to ensure that the round did not merely explode on the target aircraft's skin (which would cause little damage), but instead penetrated it and exploded when it came into contact with fuel or coolant inside the fuel tanks or radiators respectively.
Construction
MK 108 firing operation cutaway schematic
MK 108 firing operation cutaway schematic
The cannon proved to be very effective and reliable, yet comparatively light, compact and easy to manufacture. These characteristics stem from its simple construction—80% of the weapon was made from stamped parts, and the number of moving parts was kept to a bare minimum using a simple blowback operation. However, the simple blowback operation had its disadvantages.
Otherwise, it was simple to manufacture and maintain, and its compact size and weight as well as its electrical priming made it ideal for aircraft installation. The cannon's distinctive heavy pounding sound and high rate of fire gave it the nickname "pneumatic hammer" amongst Allied aircrews, amongst whom the cannon gained a fearsome reputation due to its destructive power.
[edit] Disadvantages
Normally, gas-operated or delayed-blowback mechanisms are used in automatic weapons of rifle-calibre and larger because the chamber pressure in such weapons would be very high. Therefore, if a simple blowback system (where there is no positive lock between the bolt and barrel) is used, the bolt may recoil and open the breech while the chamber pressure is still high, causing damage to the weapon and split cases (see blowback article for more information). In the MK108, this problem was eliminated by simply reducing the muzzle velocity and shortening the barrel of the weapon to the point that, by the time the expanding gases from the fired round overcame the inertia of the heavy bolt and blew back the breech, the round had already left the weapon. This therefore allowed most of the gases to escape via the barrel, dropping the chamber pressure to a safe level. The heavy bolt then continued to move backwards into large buffer springs, which then pushed the bolt back into battery after a fresh round had been fed.
The low muzzle velocity needed for this simple operation became the MK 108's main shortcoming, with the result that its projectile trajectory dropped considerably after a comparatively short range. This made effective firing ranges short and aiming a challenge.
Ammo types
Komet weapons: MK 108 cannon
MG 151 cannon
20mm
ROF 750 RPM
Muzzle velocity 2560 feet / sec
MG 151/20 specifications
Two versions of the 20 mm MG 151 were built: one with a percussion priming system and a second E-model with electrical priming. Some rounds were available with a timer self destruct and/or tracer (or glowtracer). There were also different types of High Explosive shell fillings with either standard PETN, a mixture called HA41 (RDX and aluminium), and a compressed version where more explosives were compressed into same space using large pressures (XM).
* Rifling: 1 turn in 23
* Round types:
o AP - round weight of 117 g.
o HE - round weight of 115 g. HE filler: 3.6 g
o HE(M) - Minengeschoß ("mine shell") - round weight of 92 g. HE filler: 18 g
o HE(XM) - round weight of 104g. HE filler: 25 g
o Incendiary, with either phosphorus and thermite filling.
o API (Armor piercing incendiary).