Machine Guns and Cannons (Ground, Vehicle, and Aircraft Mounted Weapons)

[Maverick]

Donny, I don't know as a 'viable' alternative.  Possibly, the 25 pounder was considered to give the tank a 'support' capability.  The Bishop had a 25lber as its main armament and there was never the suggestion that it was anything other than a support weapon.

Regards,

Mav

[rickshaw]

The difference in penetration would have been accounted for by differing testing criteria.  British and American armour penetrations are fraught with problems because they did their testing in very different ways against very different targets.  Further, the 25 Pdr was firing solid shot AP whereas the 105mm was firing HEAT.  So its a bit like comparing apples and oranges all 'round.

As to the use of the 25 Pdr as a tank weapon, in the case of the Sentinel it was the only other gun available, at the time which had superior performance compared to the 2 Pdr.  Australia only produced two guns in WWII - the 2 Pdr and the 25 Pdr.  Therefore it was a case of one or t'other.   The Australian Army was still under the delusion in 1941 that it would be fighting primarily in the Middle-East, not the Pacific and it's main foe would be German tanks.  When reports came back from North Africa that the Germans were fielding Panzer III's and IV's which were largely impervious to the 2 Pdr, they decided they needed to upgun the Sentinel.   The result was the AC III, with the 25 Pdr.   That it was a bit of an overkill was obvious when the main foe became the Japanese. 

While it obviously had considerable utility as an infantry support weapon, you must remember that was _not_ the role of cruiser tanks in the British/Commonwealth "ethos" (now called "doctrine") of battle.  They were intended for exploitation and hence engaging enemy tanks.   What that doctrine of course failed to take into account was that the primary defence against tanks were anti-tank guns and the availability of particularly HE and secondarily smoke rounds became of extreme importance, as the Germans with their 50mm armed Panzer IIIs and 75mm armed Panzer IVs demonstrated in North Africa.   When that was realised, the British/Commonwealth provided a troop of 3in Howitzer armed cruisers and infantry tank to each squadron of tanks (usually the HQ troop) and attempted to remedy the situation by first creating a co-axial mount (with both 2 Pdr and 3in in it) and then later when the American 75mm gun came along, it (interestingly, initially using captured German ammunition).   This led eventually to the quest for what Mongtomery called the "universal tank" which could do both infantry and cruiser functions in one and eventually produced the superlative Centurion.

[dy031101]

US 75mm gun using captured German ammo?  As in Pak 97/38 or...... Pak/KwK 40?

[rickshaw]

US 75mm gun using captured German ammo?  As in Pak 97/38 or...... Pak/KwK 40?

As in KwK40.  The shells were remanufactured in Cairo - they had their fuses replaced by British ones and were mated to used American shell cases which were filled with a mixture of German and British powder and given new primers.   This was detailed in Hunnicutt's book on the Sherman (available for a steal at >$250 on Ebay at various times.  Luckily mine only cost $50!  ), if you're interested.  Pak 97/38 didn't see service in North Africa but if they had, they could have used the ammunition directly.  The American M2 75mm tank gun was developed from the same famous soixante-quinze.

[dy031101]

As in KwK40.  The shells were remanufactured in Cairo - they had their fuses replaced by British ones and were mated to used American shell cases which were filled with a mixture of German and British powder and given new primers.

I wonder how they perform...... in fact the Wikipedia entry on QF 75mm used to mention an improved British AP shot for it (and, theoretically, the US 75mm), which now led me to wonder where that one came from......

[rickshaw]

As in KwK40.  The shells were remanufactured in Cairo - they had their fuses replaced by British ones and were mated to used American shell cases which were filled with a mixture of German and British powder and given new primers.

I wonder how they perform...... in fact the Wikipedia entry on QF 75mm used to mention an improved British AP shot for it (and, theoretically, the US 75mm), which now led me to wonder where that one came from......

I would suggest "adequately".  Hunnicutt does not note any reports of problems and he is perhaps the most thorough author I have ever discovered.  You get what you pay for in his books - if they were priced by the kilogram he'd make a fortune.

I'll check my copy of Hogg's "British and American Artillery of World War Two".   He'll most probably have something on it.  It might have just been an improved muzzle velocity, rather than anything exotic and that could be achieved with better or more powder.

The remanufacture of ammunition is fairly commonplace and an industrial process.  As long as care is taken, there isn't any great danger involved and often ammunition can be easily adapted to different weapons of same or similar calibre.  The Germans used to use 76.2mm rounds in 75mm guns and vice-a-versa after replacement of the driving bands.

[dy031101]

For the sake of argument, how powerful is a HE shell from the 105mm L7 compared to WWII 105mm~107mm field guns and howitzers?

[rickshaw]

For the sake of argument, how powerful is a HE shell from the 105mm L7 compared to WWII 105mm~107mm field guns and howitzers?

At a guess it would be about the same, perhaps slightly less "powerful".   In the past, most tank gun rounds have carried substantially less HE than a comparable calibre artillery weapon because of the increased stresses involved with firing them at a higher muzzle velocity.  A good example is the US 76.2mm tank gun's HE versus the US 75mm tank gun's HE rounds.  The former carried about half the HE of the latter - showing the latter's artillery heritage and also the problems of trying to make a HE round with strong enough walls to accept the increased acceleration when fired from the former.   Both are obviously nominally the same calibre. 

Nowadays tank gun designers are better at their job and design the rounds better and fire them at substantially lower muzzle velocities - cause you can have the digital fire control adjust aiming more easily than a human can.  Interestingly though, plain HE has basically disappeared from most modern tank guns of 120+mm calibre because of the space limitations such large rounds impose on their stowage.  Nowadays you get "multi-purpose" rounds, basically HEAT with electronic fusing which is set to either explode on impact (HEAT) or delay (HE) for comparable effects.  However, they invariably carry considerably less HE than a plain HE round would.  Some are designed also to have a fragmentation "sleeve" which the loader applies as they are loaded, to increase their effect against infantry.

[dy031101]

The remanufacture of ammunition is fairly commonplace and an industrial process.  As long as care is taken, there isn't any great danger involved and often ammunition can be easily adapted to different weapons of same or similar calibre.  The Germans used to use 76.2mm rounds in 75mm guns and vice-a-versa after replacement of the driving bands.

Question inspired by this: could armour penetration be notably improved by taking a "necked-down" version of a bigger gun cartridge?

[rickshaw]

The remanufacture of ammunition is fairly commonplace and an industrial process.  As long as care is taken, there isn't any great danger involved and often ammunition can be easily adapted to different weapons of same or similar calibre.  The Germans used to use 76.2mm rounds in 75mm guns and vice-a-versa after replacement of the driving bands.

Question inspired by this: could armour penetration be notably improved by taking a "necked-down" version of a bigger gun cartridge?

It can be done.  The Canadians were experimenting in WWI with a 2 Pdr gun with a 6 Pdr chamber which used a 6 Pdr case necked down to a 2 Pdr shot (57mm to 40mm) and firing a slightly hotter powder charge.  Problem is, you have to then be very careful about chamber and bore pressures or risk a blown out breech or bore.   

Once APDS was developed, the point of such a weapon disappeared 'cause suddenly you could have a full bore weapon, firing a full charge round which was effectively much smaller, denser and had a substantially higher muzzle velocity.

[dy031101]

Wikipedia claims that the Ki-45Kai Otsu is armed with a manually-loaded 37mm gun.

Interesting...... I wonder how the installation looks like and how the crew is supposed to load it......

Does anyone have illustration on how the whole thing worked?

[Maverick]

Seems funny that a 37mm weapon wouldn't be magazine fed.  If you find anything Donny, please share as it seems a complication for a comparitively small round.

Regards,

Mav

[rickshaw]

It as IIRC adapted from a relatively low velocity infantry support weapon.  It didn't perform very well because of both the manual reloading and the low initial velocity.  Useful perhaps against San Pans and other "native" craft but not terribly useful in the face of modern shipping and their AAA defences.

[Maverick]

Oh ok.  Wikipedia suggested it was taken from a tank weapon.  Definitely an odd choice for an aircraft weapon, given that Japan had the Ho-203 cannon, a 37mm weapon that was, I believe, used in other marks of the Ki-45.  Perhaps it was developed because of the deficiencies of this earlier design?

Regards,

Mav

[rickshaw]

No idea.  Japanese weapons and aircraft development choices are still not terribly well known outside of Japan.  We have the WWII intelligence reports and the post-war stuff based on them but they are always noted as having "flaws".   It might have been simple availability.  "Here's a load of old guns, lets see if we can find a use for them!"   Rather like the Mollins loader for the 6 Pdr which was developed for an SPAT, used initially on aircraft and eventually found it's niche on MGBs.