The Italian Guns.

[CharlesBronson]

For the maniac.

To be effectively synchronised, a gun required a short "lock time"; the delay between the gun receiving the message to fire and the cartridge actually firing. This had to be as short as possible, in order to provide the precision needed to avoid hitting the propeller.
A lot of MGs and cannon (the Scotti included) fired from an open bolt; the starting position for the gun was with the chamber empty and the bolt held back. When the gun received the message to fire, the bolt was released, began to move forwards, picked up a cartridge, loaded it into the chamber, locked up the action and, only then, fired. This took far too long. There were a few open-bolt guns which retained a separate control of the firing pin (the MG 17 was one) which did enable them to be synchronised.

The Breda S.A.F.A.T used a copy or the Browning short recoil mechanism...the Browning Short recoil system used in the M2/M3 caliber.50 and the M1917 M1919 cal 30 is a closed bolt short recoil mechanism.

I dont have any Idea what is your source for the Breda shooting from an open bolt but is simply WRONG.

Hai capito bene ?

 

[bruno_]

Hi Charles,
the sources of my information are the official manuals of the Breda. Therefore if there it is explained what I reported in my post, we should conclude Breda were open bolt machine guns.

As to the short "lock time" issue, as I've also said, this is one of some factors indicating the possibility for a gun to be synchronized. Most of the time is THE factor, but it is not the only one. By way of example, MK 108 30mm cannon had its unsolved synch. problems in the uneven rate of cartdrige propellant burning time.

 

[CharlesBronson]

12,7x81SR ammunition.

The ammo employed in the italia heavy machineguns was originally designed by Vickers in 1920s, after the fauilure of the "class B" Mg chambered for this round, the cartrigde was slightly modified ( from rimless to semi rimmed) and offered for export.

Both italy and Japan eventually used it in WW2.

From left to right:

a) Ball

b) FMJ Tracer

c) Armor piercing with hardened steel core

d) Incendiary

e) AP-Incendiary without tracer, both bullets had a blue tip.

There was also a fully explosive bullet with impact fuze, despite the fact many experts considered the 20mm as the minimum practical diameter for a HE shell the italians didnt agreed, and used a generous quantity of explosives in the fighters ammunition belt.
This type of projectile was indicated by a yellow band.

Muzzle velocity of the 12,7x81mm ammo varied between 750 and 771mps, projectile weight between 32 to 38,5 grams.

Reloading a Macchi MC 200.

 

[kool kitty89]

On the synchronization issue, I've also seen several refrences to the .303 Browning machine gun (version of the M1919) saying that it fired from an open bolt due to problems with "cook-off" when using the .303 British round. (with the more heat sensitive cordite) But the .303 Browning was used in Synchronized mountings in several aircraft, namely the Gladiator.

ANd here's an article on the .50 Vickers: Untitled Document (from which the Italian 12.7mm ammo was derived)

 

[CharlesBronson]

Hmm... maybe it was for wing mounting only. Where is Tony W when you really need him ?

 

[kool kitty89]

I'm not entirely sure the open bolt version was used in the Gladiator, but as you mentioned other modifications could allow an open-bolt weapon to be synchronized. (as you mentioned on the MG 17)

Electric priming (used on most German synchronized mountings, the MG 17 possibly the only exception) allows open bolt synchronization as well (assuming the mechanism its self is compatible with such a mounting) as Tony Williams mentions on synchronizing the 20 mm Hispano.

 

[CharlesBronson]

Well, Tony is the man for that type of quandacy unfortunately I havent see him around here for a while.

Mauser MG 151/20

One of the most bizarres topic of WW2 italian aircarft armament of how they failed to provide a 20mm gun. The Regia aeronautica purchased some Oerlikon "L" cannon in early 1930s for seaplanes, but just in small quantities.
They have also two army/navy AAA full automatic guns, both chambered for the german 20x138B cartrigde; the Breda 20/65 and the Isotta-Fraschini (Scotti design) 20/70, however there were no attemps to convert that weapons in airborne guns.

In lieu of a modern fast firing 20 mm cannon indigenous design for aircraft the italian purchased the Mauser reliable MG 151 and adapted it to several types of fighters.

For detailed information on the MG 151/20 and its ammunition:

http://www.ww2aircraft.net/forum/we...ftwaffe-cannons-machineguns-topic-6368-3.html

http://www.ww2aircraft.net/forum/we...ftwaffe-cannons-machineguns-topic-6368-4.html

http://www.ww2aircraft.net/forum/we...ftwaffe-cannons-machineguns-topic-6368-5.html


Reggiane Re-2001 CN, 2 Mausers under wings.

Reggiane Re-2005 2 x 20 mm Mauser in wings plus one in the engine.

Servicing the starboard Mauser in a Fiat G-55.

 

[CharlesBronson]

- Long and short gun cover in Fiat G-55 of the ANR.

- Squematic of engine and wing emplacement in Fiat G-56

- 6 x MG 151 in project Fiat G-58

 

[CharlesBronson]

Breda dal 37/54

This was the standard Italian close-range AA weapon used on larger ships during World War II. The guns used in the Model 1932 mountings were water-cooled with a recirculating pump, but the others were air-cooled. The magazines held only six rounds, but it was possible to load them one after the other and thus maintain a high rate of fire.

The adaptation for aircraft was first requested in 1941 and took place in 1943.

A single Fiat BR 20 was equipped with a 37mm gun in a solid nose, it was designated BR 20Ca ( ca for Cannoncino, aircraft cannon) . More serious attemp took place in the Savoia Marchetti SM 89 attack bombers, wich was designed to be the italian Henschel Hs-129 but faster and with better bomb load. The prototype of this model first flew in 1940, however the 37mm armed variant did it in mid 1943 when the final was close for Italy and it only remained as a experimental airplane( 2 built)

Two 37mm guns, SM 89

 

[CharlesBronson]

Data on Breda 37/54 single weapon and ammunition. The weight quoted is for the naval gun, the airborne variant was 10 % lighter. Couldnt find data about the case lenght but is stimated between 280 to 300 mm with rim.

 

[red admiral]

Tony William's website gives;

Cartridge: 37 x 232SR
Rim Diameter: 51.5
Projectile weight: HE / 799 (seems far more likely than the 1.63kg quoted by Navweaps which is heavier than 47mm projectile)
Muzzle Velocity: 800m/s

The cyclic rate of fire seems to have been around 200rpm with 120rpm being more practical from clip loading.

 

[CharlesBronson]

Tony William's website gives;

Cartridge: 37 x 232SR
Rim Diameter: 51.5
Projectile weight: HE / 799 (seems far more likely than the 1.63kg quoted by Navweaps which is heavier than 47mm projectile)
Muzzle Velocity: 800m/s

My stimated was wrong, thank you, probably the weight quoted from Nav weapons is the complete round and not only the projectile only.

Thank you again.8)

 

[CharlesBronson]

By the way, the manually operated Scotti equpped turret was not "Lancia" but Lanciani delta type 1.

 

[red admiral]

CharlesBronson,

Do you happen to have any information on a 27mm weapon? I've seen it mentioned briefly a few times but have no real information on it.

 

[CharlesBronson]

A italian 27 mm ?

No really, all I got with "7" is about a 47 mm autogun. I think it was made by Caproni.

 

[CharlesBronson]

47 mm automatic cannon:

Aparently this type was only used in the Breda 88 and the Fiat AS 14.

 

[CharlesBronson]

The 47 mm gun installed in Ba 88 (underfuselage)

Fiat AS 14 ( nose)

 

[red admiral]

Hello,

Do you have any further details on the 47mm weapon? Chinn gives a detailed explanation of how it works but no details as to weight, rate of fire etc.

Thanks

 

[CharlesBronson]

Unfortunately no much more data, I know it used the same 47mm cartrigde as the infantry 47/32 Breda AT gun, I suppose the rate of fire must be some between 100 to 120 rpm.

 

[CharlesBronson]

47 x 195 Ammunition.

As I said earlier the 47 mm automatic cannon used the same catrigdes as the infantry at gun, those were:

-APHE M35
-APBCHE M39
-HE M35
-HESH M41 EP "effeto pronto" quick effect with internal fuze.
-HEAT M41 EPM "effeto pronto meglirato", quick effect improved, a hollow charge capable to penetrate 66 mm of armor.

The high explosive ammunition had a muzzzle velocity of 450m/s and the AP 630 mps.

- From left to right: HE, AP M1935, APCbC M1939.

- Cutaway view of Arnor piercing bullets.