Breda Safat 12,7mm ammunition

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Post by Editor » Thu Jul 30, 2009 3:37 pm

Where did you get the 575 rpm from ?
Vince Tassone

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Alex T.
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Post by Alex T. » Thu Jul 30, 2009 5:04 pm

Webmaster wrote:Where did you get the 575 rpm from ?
Wikipedia of course! ;)

Joking aside, it's a datum that I remember from a Regia Aeronautica maintenance manual for aircraft weapons. I remember it vividly because I was quite shocked to see such a low rate of fire for a syncronized machinegun! :shock:

Bear in mind of course that the rate of fire wasn't absolute, it varied according to the engine revs, and in this case 575rpm is an average number. If you have a look at the outside placard on the Macchi 205 cockpit it will actually give operational speeds when to use the syncronized machineguns!

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Post by Editor » Thu Jul 30, 2009 8:21 pm

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I believe it was Wikipedia. Here's the synchronization plate you're referring to. It doesn't say anything about 575 rpm, in fact its says don't fire the cowl mounted MGs below 1000 rpm. This doesn’t add up to what you’re saying. I think you're mistaking the synchronization speeds with the Fiat Cr.32. I'm not buying what you're saying, the ballistics speak for themselves and the Breda-SAFAT as I've already mentioned was an effective weapon, its pilots found it reliable and it continued to be used on Italian fighters throughout WWII. The SAFATs effective range was more than twice that of the British fighters and its striking power was approximately equal to similar guns used by Germany and Japan.

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Here's another table that takes into account the rpms and the amount of metal delivered to target. As you can see, each 0.5 in gun delivers about a 1lb of metal per second. After a 10s burst its about 10 lbs. So lets say a RA pilot squeezed the trigger a little longer than the 10s, he gets a little more, maybe a little more than an Allied pilot who didn’t squeeze the trigger as long, but not a whole lot more. My point is, I don't think you can hang your hat on rpm because the differences, in practical terms, are negligible.


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Here's an English pilots account of being shot-up by Macchis over Malta. As you can see, the pilot had the wits scared out of him and his aircraft badly damaged by SAFAT HE rounds. Also, do keep in mind, that the kill/sortie ratio was the same for RA pilots as it was for US and Commonwealth pilots. If equipment was deficient as you suggest, then this would have been borne out in this figure.

I really don’t know what else to say here. I think you’ve bought into too many of the WWII myths. Perhaps you need return to Italy - or probably not :)
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Post by Alex T. » Fri Aug 07, 2009 5:35 pm

Ok, as promised I worked on a more accurate study on the Breda SAFAT 12,7mm machinegun and its ammunition, the 12,7x81mm SR (semi rimmed).
I divided my study in three parts, the data available, the machinegun and ammunition performance, the practical use of the guns.

All these informations have been gathered from original manuals, ammunition specialised websites and servicing manuals.

So here we go, let's start with some info:

AVAILABLE DATA

Machinegun info

Model: Breda SAFAT 12,7mm
Type: Gas operated machinegun
Calibre: 12,7mm (0,50in)
Weight: 29 kg
Muzzle speed: 762 m/s* (average)
Rate of fire: 700 rpm without syncronization mechanism
575 rpm** with synchronisation mechanism
Sync system: mechanical
Feeding: Self destructing metal links
Hitting power: 9.93 Kjoule


*the muzzle speed was affected by several factors: bullet shape (HE being slower and heavier than other “spitzer” balls); muzzle temperature; G-loads; airstream contrary to the bullet vector.

**this rate of fire is actually an average figure calculated according to the evaluated performance of the syncronized machinegun on different Regia Aeronautica aircrafts. The rate of fire would vary according to the propeller revs, and would go as down as 380 rpm, or as high as the normal unsyncronized rate.


Ammunition info

Model: 12,7x81SR, based on the Vickers .5”V/565
Calibre: 12,7mm
Case: Semi rimmed, 81mm
Weight: 565 grains (36,5gr) (average)
Bullets: AP, API, API-T, I-T, HE and HEI-T

all the bullets but the HE and HEI-T had a spitzer shape (pointed), some of them had a smooth surface, other presented seams because the ball was actually composed by two parts. The HE and HEI-T had a circa 12.3 grains (0,8gr) of explosive charge known as Penthrite wax.



THE MACHINEGUN AND AMMUNITION PERFORMANCE


The Breda SAFAT was developed after the adoption of the British Vickers ammunition: the short-recoil system meant the weapon weight was considerable (it was the heavier of machineguns that used that specific ammunition) and the rate of fire of 700 rounds per minute, although respectable, was seriously inferior to the similar heavy machineguns of the era (the Ho-103, developed by Japan as a shorter version of the US .50” Browning and using the same ammunition, was capable of 900 rounds per minute and weighted only 22kg).
The typical installation of the Breda SAFAT was on the engine cowl area, meaning that most of the times it actually was a syncronized machinegun.
The reliability of the weapon was good to very good: the low rate of fire and the heavy belt guaranteed a relatively low number of jams, although environment factors like sand would undermine the reliability level.



The variety of bullets used on the Breda SAFAT was considerable: the Allies gave up on the development of explosive bullets, because they reckoned that the effectiveness with such relatively small calibre would have been insignificant. On the other hand, the Axis forces all developed their own versions of the bullets, with different results.

Ball – API – API-T and HEI-T sections

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It is important to note that the different muzzle speed, bullet weight and centre of gravity of each kind of ammunition meant the ballistic characteristics of the bullet were specific to the model; this means that in a burst that contained all the kinds of ammunition, the bullets would behave in a different way: some would have flown further, some would have had more penetration power, some would have been more accurate than others.

There is a debate whether the use of explosive ammunition on such relatively small calibre would have been effective: the Allies decided not to use it in such calibre, aiming for a more precise weapon system, while the Axis forces all used them. The Germans developed a seried of 13mm ammunition (MG131) which had the same variety of bullets, with the main difference that the rate of fire of the MG131 and also of the Japanese Ho-103 were higher, even in syncronised installation, to the Italian Breda SAFAT.

THE PRACTICAL USE OF THE GUNS

The typical installation of the Breda SAFAT 12,7mm would have been a couple on the engine cowl area, supported by the Breda SAFAT 7,7mm on wings or, in later examples, of 20mm cannons MG151/20.

The first thing that one notices on the Italian choice of armament is the quantity of weapons: the Allies opted for at least 3 .50in machineguns per wing, the Axis used 2 cowl 12,7mm machineguns supported by at least 2 20mm cannons.

They were two completely different approaches:

the Allied one was to concentrate the fire of 6 or more machineguns in a single spot and with a high rate of fire, counting on the ballistic performance of the bullets and the incredible power of converging machineguns. It could be considered a versatile and dynamic kind of shooting, where the ammunition characteristics allow the weapon system to be effective even on long distances.

The Axis one was a more "on demand" approach: according to the target and combat situation, the pilot could choose to use weapons that had a relatively low rate of fire but extreme punch (the 20mm cannons) or "whip" the enemy with the heavy machineguns, not as devastating as the 20mm shells, but still with plenty of effective ammunition delivered at a high rate of fire.

To sum it up, the Allies tried to deliver a high hitting power by the converged hit of 6 or more machineguns, while the Axis tried to do the same counting on the bullet performance.

Both system proved effective, it was a matter of knowing how to use it.

The Italians instead seemed to lack of a "main punch" gun, either bullet effective or performance effective.

Having a low rate of fire and bullets there were not as performing as the 20mm ones meant that to achieve the same hitting power, an Italian fighter pilot should have hit the enemy with longer bursts. Using the following chart

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let's try and make an example:

A P-40 (6x .50in) and a Macchi 202 (2 x Breda SAFAT 12,7 + 2 x Breda SAFAT 7,7) shoot a 1 second burst at each other, what are the results?


a 1 second burst of 6 M2 .50in machineguns converged at X yards, would have delivered in the converging point an impressive 75 bullets, of which circa 12 of them tracer ammo, developing 1,517.25 Kjoules.

the same 1 second burst from the Macchi would have delivered 19 12,7mm rounds and 28 7,7mm rounds. The former would have developed 188.67 Kjoules, the latter 103,04 Kjoules, for a total of 291.71 Kjoules.

This means that to match the effectiveness of a 1 second burst of the P-40, the Macchi should have hit the target with a 5,2 seconds burst.

As you can easily imagine, it's going to be easier to hit a high speed flying target with a 1 second burst that with a long 5 seconds one, which means that to be as effective as their counterparts, the Breda SAFAT needed to hit their target 5 times more than their enemy.

I simplified many aspects of the debate, like every single bullet performance, penetration factor etc.. but the most important result that we found out is that the Breda SAFAT might have well been reliable and sturdy weapons, but they weren't effective when it came to their performance, if compared to the other available machineguns.

This again doesn't mean that the weapons were necessarily bad, but it meant that pilots had to make a bigger effort to shoot down enemy planes, because their weapon efficiency was a fifth of what the enemy had available at the time.


I hope this post is more clear than the previous debate. Once again I am interested in the opinion of you all and would like to exchange your ideas about it.

Cheers

Alex

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