OctavianAvgvstvs

47/40 anti-tank cannon - muzzle velocity and penetrations = correct?

Hi everyone,

 

I was looking at the famous Military Guns & Ammunition by Anthony Williams website (the "bible" of cannon-related stuff),

and looked at the muzzle velocity of the 47/40 cannon installed in the M15/42 and the AB43.

 

1st thing to consider = muzzle velocity
The case of the round was pretty big. It went from a case long almost 200mm from the 47/32 to a one about 328mm (!).

There are no photos related to this shell, but it's close to the "Class P" RAF airgun.
As a comparison....
PgunTank.jpg

(from left): British 2 pdr No.2 tank/AT (40 x 304R); Soviet 45 mm tank/AT (45 x 310R);   47 mm Class P gun (47 x 326R); 3 pdr Hotchkiss naval (47 x 376R); German 5 cm KwK 38 L/42 (50 x 289R); 5 cm PaK 38 / KwK 39 L/60 (50 x 419R)
Italian 47/40 should be very similiar (in lenght, as we don't know the width of the case...) to the 47mm Class P gun

Muzzle velocity is described here (http://www.quarryhs.co.uk/ammotable6.html) as 820 m/s. In game it's about 750 m/s. In Wikipedia 900 m/s.

Which is right? I don't have any data, so I am asking any expert here.

2nd thing = penetration

Can the penetration for a 820 m/s or 900 m/s 47mm round be so low? 
 

3nd thing = the Wikipedia info
In Wikipedia (italian and english) articles, it's stated that the muzzle velocity was 900 m/s (?), but the penetration characteristics

are exactly those as in-game:
".....Armor Penetration AP (L/40 Variant for Medium tank M15/42): 70 mm at 100 m, 50 mm at 500 m, 38 mm at 1000 m, 25 mm at 1500 m, 20 mm at 2000 m...."

In the italian Wikipedia , instead... they give these spec:
".... 112 mm at 100m,  80 mm at 500 meters, 43 mm at 1000 meters, and 24 mm ar 2000 meters..."

These seem more realistic. If indeed this thing fired a projectile of about 5cm at 900 m/s, it wouuld be similiar to a Japanese high-power 47 or not too dissimilar from a KwK 50mm.
A slightly less powerful version of the 6 pounder ...

 

Any ideas? Data?
Thanks!

 

Edited by OctavianAvgvstvs
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16 minutes ago, LordNemoII said:

As already said a lot of times, the current values in the game are placeholder.

They will be fixed, just wait.

SOONtm

Wonder if most of the values for British guns are placeholders too? They aren't correct either :D

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20 minutes ago, AtomicPope said:

They have a very large amount of filler for an APHE round which can reduce the penetration, though I don't know by how much.

In game the 47/40 has not a APHE shell, but an APBC....

 

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2 hours ago, paulassos5 said:

In game the 47/40 has not a APHE shell, but an APBC....

 

It is still an Armour-Piercing round filled with HE, its just has a ballistic cap.

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19 hours ago, Time4Tea said:

It is still an Armour-Piercing round filled with HE, its just has a ballistic cap.

Then a standard aphe would have a little more pen? Like the 47/32 aphe has 54 at 10 meters while the 47/32 apbc has 53 at 10 meters. Co be possible? 

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5 hours ago, MadMax_ITA_ said:

Then a standard aphe would have a little more pen? Like the 47/32 aphe has 54 at 10 meters while the 47/32 apbc has 53 at 10 meters. Co be possible? 

AFAIK a ballstic cap is there to reduce drag and retain the muzzle velocity of an AP round so it shouldn't really negatively affect penetration (especially since the M.V. of the Mod.35 and Mod.39 rounds are the same in this regard) but it shouldn't improve performance against slopes either. The wierd thing between those two 47mm rounds as that the one with the ballstic cap weighs 100 grams less than the one without.

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2 hours ago, Time4Tea said:

AFAIK a ballstic cap is there to reduce drag and retain the muzzle velocity of an AP round so it shouldn't really negatively affect penetration (especially since the M.V. of the Mod.35 and Mod.39 rounds are the same in this regard) but it shouldn't improve performance against slopes either. The wierd thing between those two 47mm rounds as that the one with the ballstic cap weighs 100 grams less than the one without.

Pretty sure the ballistic cap won't improve close range slope performance but the reduced drag should allow it to retain better sloped performance at range than an uncaped shell

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Excuse my ignorance on the subject, there is no image of the 47 mm bullet used the on 47/40? if I'm not mistaken it was bigger than the one used since 47/32 ...

In the game both cannons shoot a 1.4 Kg projectile, but if the 47/40 had a larger cartridge, should not even have a heavy bullet?

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I know, I ask If the projectile used on 47/32 gun is the same used on 47/40 gun, because the 47/40 gun used a larger cartridge.

 

 

I hope I explained myself, I apologize but my English is poor.

 

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16 minutes ago, paulassos5 said:

I know, I ask If the projectile used on 47/32 gun is the same used on 47/40 gun, because the 47/40 gun used a larger cartridge.

 

 

I hope I explained myself, I apologize but my English is poor.

 

Same 47x195mm cartridge 

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39 minutes ago, *gaelan said:

Same 47x195mm cartridge 

Are u sure? Look at there...

 

On 08/01/2019 at 16:33, OctavianAvgvstvs said:

1st thing to consider = muzzle velocity
The case of the round was pretty big. It went from a case long almost 200mm from the 47/32 to a one about 328mm (!).

There are no photos related to this shell, but it's close to the "Class P" RAF airgun.
As a comparison....
PgunTank.jpg

(from left): British 2 pdr No.2 tank/AT (40 x 304R); Soviet 45 mm tank/AT (45 x 310R);   47 mm Class P gun (47 x 326R); 3 pdr Hotchkiss naval (47 x 376R); German 5 cm KwK 38 L/42 (50 x 289R); 5 cm PaK 38 / KwK 39 L/60 (50 x 419R)
Italian 47/40 should be very similiar (in lenght, as we don't know the width of the case...) to the 47mm Class P gun

Muzzle velocity is described here (http://www.quarryhs.co.uk/ammotable6.html) as 820 m/s. In game it's about 750 m/s. In Wikipedia 900 m/s.

Which is right? I don't have any data, so I am asking any expert here.

 

 

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5 hours ago, paulassos5 said:

I know, I ask If the projectile used on 47/32 gun is the same used on 47/40 gun, because the 47/40 gun used a larger cartridge.

 

 

I hope I explained myself, I apologize but my English is poor.

 

 

The projectile is the same, what's different is the amount of propellant. Larger cartride=more propellant to make the same projectile faster and thus gain in penetration. To compare, just look at german 75mm tank guns, the projectile weighs more or less the same for all of them, regardless if it's a KwK 37 L/24, or a KwK 42 L/70 - however, the L/70 has a much longer cartridge with much mure propellant, thus having much more muzzle velocity and penetration.

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13 hours ago, AtomicPope said:

 

The projectile is the same, what's different is the amount of propellant. Larger cartride=more propellant to make the same projectile faster and thus gain in penetration. To compare, just look at german 75mm tank guns, the projectile weighs more or less the same for all of them, regardless if it's a KwK 37 L/24, or a KwK 42 L/70 - however, the L/70 has a much longer cartridge with much mure propellant, thus having much more muzzle velocity and penetration.

 

 

I think I understand, so from what I can understand the 47/40 cannon was developed to accommodate a larger cartiridge (from 195 mm to 328 mm) and shoot the same projectile.

Well undoubtedly the result is better but with more than a third of propellant is not that the cannon becomes exceptional.

I'm not an expert, but it seems a little bit, don't you find it too?

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14 hours ago, AtomicPope said:

 

The projectile is the same, what's different is the amount of propellant. Larger cartride=more propellant to make the same projectile faster and thus gain in penetration. To compare, just look at german 75mm tank guns, the projectile weighs more or less the same for all of them, regardless if it's a KwK 37 L/24, or a KwK 42 L/70 - however, the L/70 has a much longer cartridge with much mure propellant, thus having much more muzzle velocity and penetration.

KwK 37 used pzgr Rot with wasn't designed to handle high velocities..

 

Pzgr 39 used by KwK 40 and KwK 42 was the same (albeit with changes made over years)

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The MV is correct according to original German documents.

 

T2AbRFt.jpg

 

Even if the penetration is somewhat correct at 30° (50mm at 500m), the vertical penetration is slightly underperforming.  

 

AYjjbgH.jpg

 

If we took the penetration values of WWII Ballistics Armor and Gunnery and increased the MV via DeMarre, we'd get 74mm at 100m (which is still 10% higher than the value we have right now in-game).

 

ku8Gbyy.jpg

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