This is intended for people interested in the subject of military guns and their ammunition, with emphasis on automatic weapons.
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I haven't visited this forum in a while and ... Wow! Has changed a lot!
I have recently been playing with IL-2 Desert Wings and this simulator offers the possibility to decide the type and sequence of ammunition for each and every weapon. I am interested in the pair of Breda-SAFAT 12.7 mm that armed the Italian fighters and I was wondering what could be the best (and more historically correct) combinations for, respectively, air-to-air combat against fighters and bombers, and ground strafing (I presume soft targets).
This is the arming screen: on the left is the existing combination (here for the first gun), on the right is the list of available cartridge types.
Can you help me?
P.S.: it seems to me that the image is too small; here are the enlargements of the left and right side.
The only info I have on this ammo can be found in this article (with nice sectioned examples of the rounds). I have no information about ammo belt composition.
At first glance, though, please let me point out a tiny correction: "Società" instead of "Societas". Moreover, allow me to dissent about "superior, aircraft gun, the 12.7 mm Ho-103 (based on a smaller version of the .50 Browning M2)" since, in the use the Japanese did of it, that's to say synchronized, its rate of fire was a poor 400 rounds per minute, against the 574 rpm of the Italian Breda-SAFAT 12,7 mm, thanks to the "sblocco dell'otturatore tramite il meccanismo a leva di Mascarucci (release of the bolt through the Mascarucci lever mechanism)". Besides, the M2 from which the Japanese gun derived had an even worse synchronized RoF (300 rpm) cause its longer cartridge if compared to the Italian/Japanese one.
Anyway, lacking historical information, I would like to learn the basic about different scope of ammunition, if you could give me some hint. Leaving apart the obvious tracer and incendiary, what's the scope of an AP against an aircraft, I wonder, and what's the objective of an HE? What about a criterion to set an ammo belt composition?
First, I have noticed an error in that article: the Japanese Brownings like the Ho-103 were not based on the Browning M2, but the earlier Model 1921.
I wouldn't get too worried about the exact rate of fire - this could vary quite a lot depending on the circumstances, and any figure quoted can only be an approximate average. The quote below is from THIS article:
A practical example of the effect of synchronisation is graphically provided by comparative tests held by the USN in 1926/7 of the .30 inch (7.62 mm) M1921 and .50 inch (12.7 mm) M1921, both on a test stand and in synchronised mountings. These also shed some light on the differences between claimed and actual rates of fire, and between different installations of the same gun. The .30 had a claimed RoF of 1,200 rpm, but proved capable of between 800 and 900 rpm on the test stand. When synchronised, the RoF went down to an average of 730 rpm (a fall of about 15%), with a range of between 667 and 818 rpm for different installations and propeller speeds. The .50 had a claimed RoF of 600 rpm, and did rather well to achieve between 500 and 700 rpm, depending on the recoil buffer adjustment (although a contemporary British report put this at 400-650 rpm, the difference possibly caused by belt drag when installed), but this fell to an average of 438 rpm when synchronised, varying between 383 and 487 rpm. As the synchronised guns were adjusted for maximum RoF, this represented a reduction of around 37%. There is no inherent reason why a larger calibre weapon would suffer a bigger reduction in RoF, so the synchronisation conditions must have been better suited to the .30 in gun's natural RoF.
The ammunition mix in a belt depends upon the likely targets and also the calibre, to some extent. With a sufficiently large and powerful projectile, it is easily possible for it to possess good penetration plus contain plenty of HE and incendiary material. As the size of the projectile decreases, so it becomes less effective at everything, so there needs to be more specialisation into AP, HE and I elements (and tracer too, if required). Most air forces seemed to settle on 20mm as being the smallest to have a really effective HE load. The US didn't really bother with HE in .50 cal, apart for some experiments. They eventually settled on API as standard, but the incendiary element was very small compared with the RAF's 20mm SAPI.
Thanks again, Tony, for your patience and kind availability. Reading your notes, I realize how I would need some rudimentary about terminal ballistic in air-to-air gunnery. I still can't figure why the AP projectile was so spread in that use being the aircraft generally a "soft" structure - maybe to pierce pilot-protecting armor? Or to penetrate and damage engine?
Possible reasons for significant presence of AP.
Thanks Jeff, what you propose are all valid reasons, and I agree with them. But I would like to know the official reasons for these choices, perhaps from some manual of the time, training course, treatise or similar. Unfortunately, I can't find any.