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So the 1357's gun is odd


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Hurk #21 Posted Apr 17 2018 - 05:50

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the issue with the WW2 era 57MM rounds is that they were too light and bled off pen very quickly, dispite having a huge pen advantage over 75mm guns at close range. 

 

but much like the .22 calibre pistol and the .223 rifle, making the round longer added back the weight without losing most of the other characteristics. post war, 57mm guns can actually be heavier rounds than 75mm rounds of WW2 era, while also being much more able to pen. 

 

the one area they did fail badly, was shell normalization. post war designs for 90+mm shells for grabbing onto armor and correcting their angle of impact required a wider physical round. this is why most modern MBT weapon systems are 100-120mm sized. 



BillT #22 Posted Apr 17 2018 - 17:22

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View PostKenshin2kx, on Apr 16 2018 - 23:29, said:

 

So basically, the back or rear of the turret would house a breech loading low velocity mortor that can actually angle forward at something like 60 degrees and backwards at say a modurate minus degree depression ... so this arrangement shouldn't take up too much internal turret room, and due to the low pressure design should also be fairly light and compact. 

 

So, picture a turret with a low hanging blister on the back with a mortar like tube that can face forward enough for assisted high trajectory, high explosive rounds that can be used in front, pivot to the side and straight back in a pinch to lob ... what amounts to a large explosive grenade at a target.  In terms of range? ... think very large mortar that happens to have a very stable vehicle mount (that is also modified for breech loading from within the protection of the turret blister).  Now, granted there would still need for good crew coordination, but that would be where training comes in ... as the cost for expanded vehicle versatility. 

 

 

That basic concept was actually attempted, in a sense. The Char B had a (relatively) high-velocity 47mm gun in the turret and a very stubby 75mm howitzer in the hull.   The first Churchills had a 2-pounder in the turret and a 3 in howitzer in the hull.  Neither had very high elevation, though, and the limited firing arc made them pretty useless.  The Churchill Mk II deleted the howitzer.

 

Of course, both these attempts were limited because of the limited turret size possible at the time.  The French tank was simply an old design; the Churchill suffered from British requirements that the tank be narrow enough to fit through Britain's smaller railroad tunnels, which limited the diameter of the turret ring.  With small turrets there was no choice but to mount the howitzer in the hull, where room could be made available. 

 

The idea of a mortar in the turret rear is interesting, so let's explore it.   And I'm going to choose the KV as the vehicle for the experiment; it has the proven ability to mount the large KV-2 turret for the 152mm gun, so we can re-imagine that with a shorter, narrower turret, stretched way out with a big bustle for the mortar.  (It can be narrower because the 57mm gun is smaller and easier to load.)  Picture something like a short King Tiger turret.  Hopefully the turret can be long enough to permit crewmen to work safely between the 57mm breech (at full recoil) and the mortar.  You'll probably need a second loader for the mortar, and I'll assume the gunner can aim both weapons (he will need dual sights, of course.)  

 

Bear in mind, the service life of this tank will be short. I think 1939-1940 is the earliest you could design a tank with such a big turret, and by 1945  you have the 122mm gun in a turret, so the mortar because superfluous. 

 

I suggest that the smallest mortar worth the effort would be the Soviet PM-38 120mm mortar.   We'll assume it can be modified to a breech-loading configuration.  This was an excellent weapon and largely inspired Germany to build their own version.  Range was up to 6 km, far more than you'd need for the tank version.  (Which might enable you to shorten the barrel a bit and/or reduce the size of the ammunition.)   Here's a photo that includes people, for scale.

 

 

You can also see the size of the round.  Twice that is the absolute minimum space the mortar's breech would require inside the tank (twice, because you need space behind the breech to load the round.)  I take back what I said about the turret needing less height; at least in the rear, it's going to need to be taller than the normal KV-1 turret, especially to include the pivoting mechanism.  And you don't want to drive around with the mortar pointing up all the time, because it will snag branches and limit the under-passes you can drive through.  You're going to want to be able to fold the mortar flat on the turret roof for travel, so now I'm picturing sort of a dome on the turret rear to allow that.  That creates whole new problems: you need to armor it, and it needs a mantlet to make it bulletproof -- not to mention, waterproof.  The turret roof will require far more bracing than normal to withstand the recoil.

 

So this is probably also the largest mortar you could mount in the turret roof.  The next size up would be the Soviet 160mm M1943 mortar.  This was a breech-loader because nobody could lift the 40 kg bomb to the top of the 3 meter barrel.   That's just too big for a secondary gun.

 

And you have to store ammo.  The 57mm rounds are smaller than the 76mm rounds the KV was designed for, but they also have a higher rater of fire so you'd need to store more of them.  The 120mm mortar rounds weigh more than 76mm rounds, are larger in diameter, but a bit shorter.  Even with the bigger turret I think you're going to be cramped for ammo space.

 

I think it could work.  I still doubt it would have been very useful.  Ultimately WWII was won by medium tanks with 76mm guns, and every nation settled on that as the optimum caliber, with the USSR, always a step ahead, finally moving up to 85mm.

 



ledhed14 #23 Posted Apr 17 2018 - 17:59

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You need read up a bit on guns of WWII and The wars in the middle East . the 57 mm was a tank killer for all sides against Germany and after the war was still used in regional conflicts , to include recoiless rifles that still are around TODAY . The French and RU -Soviet versions , the ZIS being a tank killer specialist for them as well as anti air . High velocity small round , same as at the range it works , its fault being losing effectivness at longer ranges faster than heavier rounds .

.22 cal and 5.56 mm ( .228 ) is what you use today , put a .22 long rifle next to a NATO round 5.56 and examine the rounds . Now think of the 57 mm as a 5.56 mm Round with the 30 cal case used in a full size ( 30-06) neck it down for .228 and pen 3/4 " steel plate same as 30 and 50 cal AP . 



Kenshin2kx #24 Posted Apr 17 2018 - 18:49

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View PostBillT, on Apr 17 2018 - 06:22, said:

 

That basic concept was actually attempted, in a sense. The Char B had a (relatively) high-velocity 47mm gun in the turret and a very stubby 75mm howitzer in the hull.   The first Churchills had a 2-pounder in the turret and a 3 in howitzer in the hull.  Neither had very high elevation, though, and the limited firing arc made them pretty useless.  The Churchill Mk II deleted the howitzer.

 

Of course, both these attempts were limited because of the limited turret size possible at the time.  The French tank was simply an old design; the Churchill suffered from British requirements that the tank be narrow enough to fit through Britain's smaller railroad tunnels, which limited the diameter of the turret ring.  With small turrets there was no choice but to mount the howitzer in the hull, where room could be made available. 

 

<Kenshin2kx>  Actually I began this 'what if' questioning with the M3 Lee ... :D  so, I would guess a similar idea with perhaps somewhat different engineering constraints or deficiencies ... as you pointed out the hull  mounted howitzer was awkward placement and limited arc made them less than value added ... no consider if we were to start with a fresh blank sheet to address a few points ... 

 

The idea of a mortar in the turret rear is interesting, so let's explore it.   And I'm going to choose the KV as the vehicle for the experiment; it has the proven ability to mount the large KV-2 turret for the 152mm gun, so we can re-imagine that with a shorter, narrower turret, stretched way out with a big bustle for the mortar.  (It can be narrower because the 57mm gun is smaller and easier to load.)  Picture something like a short King Tiger turret.  Hopefully the turret can be long enough to permit crewmen to work safely between the 57mm breech (at full recoil) and the mortar.  You'll probably need a second loader for the mortar, and I'll assume the gunner can aim both weapons (he will need dual sights, of course.)  

 

<Kenshin2kx>  A second loader ... probably, an extra pair of hands in this case (if given sufficient room, would be beneficial I think) ... now as for caliber, I was envisioning something along the lines of 100 mm range ... potentially more HE delivery ... with much lower pressure (which enables degrees of engineering compactness that make it possible for man portable mortars)  .. now in reflection, the inclusion of a breech load mechanism does solve some problems but brings up a more basic question ... so, the idea is portable artillery - so, a traditional howizer would be ruled out due to size, weight and space considerations ... mortars add advantages, but breech loading would be far better than barrel drop.  So, how about scaling up the idea of an actual grenade launcher?  So if you take something like a Mk 19 and scale back the propellant pressure, while increasing caliber for greater HE/Shaped Charge delivery ... in essence you would have an automatic 'mortar' like weapon that if the Mk 19 is any example, should be sizable for the rear segment of a generous turret overhang?  Also scale back the automatic function in favor of single shot autoload for aimed followup shot  say, a 3 shot magazine that can be topped off by the aux gunner.  Size and weight?  Granted the caliber would  indicate a need for storage consideration, but given the very low pressure design, the shell themselves should be a fairly minor fraction of a true cannon round.  IIRC the 40 mm grenade round i like 1-2 pounds?  A 100 mm mortar shell in the range of 20 lbs ... so an upscaled 100 mm grenade round? - say 20-25 lbs?  

 

Bear in mind, the service life of this tank will be short. I think 1939-1940 is the earliest you could design a tank with such a big turret, and by 1945  you have the 122mm gun in a turret, so the mortar because superfluous. 

 

<Kenshin2kx>  I am thinking that the turret, might need to be somewhat larger ... but given the clarified context of the potential compactness of a low velocity grenade launcher (yes, I freely admit, not artillery in the strictest sense) ... but a weapon that can duplicate a fair amount of artillery functionality ... yet at a likely fraction of the size, weight and pressure/recoil concerns ... were a true howitzer used.   So, I agree, scratch the old school howitzer ... morter, closer to the goal but deficient in key areas ... so semi automatic grenade launcher of respectable caliber (100 mm range) ... granted 120mm (or larger) would be more effective, but size/weight ripple effect would start to become really ugly, at a guess.

 

I suggest that the smallest mortar worth the effort would be the Soviet PM-38 120mm mortar.   We'll assume it can be modified to a breech-loading configuration.  This was an excellent weapon and largely inspired Germany to build their own version.  Range was up to 6 km, far more than you'd need for the tank version.  (Which might enable you to shorten the barrel a bit and/or reduce the size of the ammunition.)   Here's a photo that includes people, for scale.

 

 

You can also see the size of the round.  Twice that is the absolute minimum space the mortar's breech would require inside the tank (twice, because you need space behind the breech to load the round.)  I take back what I said about the turret needing less height; at least in the rear, it's going to need to be taller than the normal KV-1 turret, especially to include the pivoting mechanism.  And you don't want to drive around with the mortar pointing up all the time, because it will snag branches and limit the under-passes you can drive through.  You're going to want to be able to fold the mortar flat on the turret roof for travel, so now I'm picturing sort of a dome on the turret rear to allow that.  That creates whole new problems: you need to armor it, and it needs a mantlet to make it bulletproof -- not to mention, waterproof.  The turret roof will require far more bracing than normal to withstand the recoil.

 

So this is probably also the largest mortar you could mount in the turret roof.  The next size up would be the Soviet 160mm M1943 mortar.  This was a breech-loader because nobody could lift the 40 kg bomb to the top of the 3 meter barrel.   That's just too big for a secondary gun.

 

And you have to store ammo.  The 57mm rounds are smaller than the 76mm rounds the KV was designed for, but they also have a higher rater of fire so you'd need to store more of them.  The 120mm mortar rounds weigh more than 76mm rounds, are larger in diameter, but a bit shorter.  Even with the bigger turret I think you're going to be cramped for ammo space.

 

I think it could work.  I still doubt it would have been very useful.  Ultimately WWII was won by medium tanks with 76mm guns, and every nation settled on that as the optimum caliber, with the USSR, always a step ahead, finally moving up to 85mm.

 

<Kenshin2kx>  I think that the idea has potential ... it would need work, and ruthless scrutiny, but I then fall back to the idea ... for infantry or vehicle ... is it value added to have an effective means of extending either the range or 'route' of firing?  I would think that it would ... the common denominator here would be the humble grenade as it translates from hand thrown, to rifle launced to vehicle mounted.   Imagine the potential for a forward armored unit having the discretional capacity to address a range of indirect fire solutions ... without being held to the mercy of a mandatory air strike or dedicated artillery bombardment?  

 

Now it goes without saying that all options should be available for best fit usage ... I do believe though that such a tank design would significantly augment the 'lower end' in terms of an arty like function IRL ... BVR - non hardened building or structure, check .. anti personel, check, soft to medium armored targets, check ... rearward tank self defense or offensive augmentation as complimentary to the high velocity cannon and mgs ... as I said, I see design potential for a more versatile armored combat vehicle tasked with multiple roles as dictated by a variety of contexts.

 

 



ket101 #25 Posted Apr 18 2018 - 03:49

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View PostBillT, on Apr 18 2018 - 02:22, said:

 

That basic concept was actually attempted, in a sense. The Char B had a (relatively) high-velocity 47mm gun in the turret and a very stubby 75mm howitzer in the hull.   The first Churchills had a 2-pounder in the turret and a 3 in howitzer in the hull.  Neither had very high elevation, though, and the limited firing arc made them pretty useless.  The Churchill Mk II deleted the howitzer.

 

Of course, both these attempts were limited because of the limited turret size possible at the time.  The French tank was simply an old design; the Churchill suffered from British requirements that the tank be narrow enough to fit through Britain's smaller railroad tunnels, which limited the diameter of the turret ring.  With small turrets there was no choice but to mount the howitzer in the hull, where room could be made available. 

 

The idea of a mortar in the turret rear is interesting, so let's explore it.   And I'm going to choose the KV as the vehicle for the experiment; it has the proven ability to mount the large KV-2 turret for the 152mm gun, so we can re-imagine that with a shorter, narrower turret, stretched way out with a big bustle for the mortar.  (It can be narrower because the 57mm gun is smaller and easier to load.)  Picture something like a short King Tiger turret.  Hopefully the turret can be long enough to permit crewmen to work safely between the 57mm breech (at full recoil) and the mortar.  You'll probably need a second loader for the mortar, and I'll assume the gunner can aim both weapons (he will need dual sights, of course.)  

 

Bear in mind, the service life of this tank will be short. I think 1939-1940 is the earliest you could design a tank with such a big turret, and by 1945  you have the 122mm gun in a turret, so the mortar because superfluous. 

 

I suggest that the smallest mortar worth the effort would be the Soviet PM-38 120mm mortar.   We'll assume it can be modified to a breech-loading configuration.  This was an excellent weapon and largely inspired Germany to build their own version.  Range was up to 6 km, far more than you'd need for the tank version.  (Which might enable you to shorten the barrel a bit and/or reduce the size of the ammunition.)   Here's a photo that includes people, for scale.

 

<picture snipped>

 

You can also see the size of the round.  Twice that is the absolute minimum space the mortar's breech would require inside the tank (twice, because you need space behind the breech to load the round.)  I take back what I said about the turret needing less height; at least in the rear, it's going to need to be taller than the normal KV-1 turret, especially to include the pivoting mechanism.  And you don't want to drive around with the mortar pointing up all the time, because it will snag branches and limit the under-passes you can drive through.  You're going to want to be able to fold the mortar flat on the turret roof for travel, so now I'm picturing sort of a dome on the turret rear to allow that.  That creates whole new problems: you need to armor it, and it needs a mantlet to make it bulletproof -- not to mention, waterproof.  The turret roof will require far more bracing than normal to withstand the recoil.

 

So this is probably also the largest mortar you could mount in the turret roof.  The next size up would be the Soviet 160mm M1943 mortar.  This was a breech-loader because nobody could lift the 40 kg bomb to the top of the 3 meter barrel.   That's just too big for a secondary gun.

 

And you have to store ammo.  The 57mm rounds are smaller than the 76mm rounds the KV was designed for, but they also have a higher rater of fire so you'd need to store more of them.  The 120mm mortar rounds weigh more than 76mm rounds, are larger in diameter, but a bit shorter.  Even with the bigger turret I think you're going to be cramped for ammo space.

 

I think it could work.  I still doubt it would have been very useful.  Ultimately WWII was won by medium tanks with 76mm guns, and every nation settled on that as the optimum caliber, with the USSR, always a step ahead, finally moving up to 85mm.

 

 

You're assuming the use of the same type of round.  The muzzle loaded mortar shell is a bit different from what a breech loaded mortar shell could be (though some trench mortars in WWI used more gun shell-like projectiles and rifling even though they were muzzle loaded.  The shells had studs that fitted into the rifling, so they weren't high rates of fire).  Muzzle loaded mortars (of the above type) require a smoothbore barrel and sufficient windage to allow the round to drop quickly enough to set off the igniter cap in the tail of the bomb.  A breech loaded tank mortar could use a much more shell shaped round, with tighter tolerances and rifling to provide stabilisation.  That means a much shorter round, and less propellant required to achieve the same results, along with a shorter barrel.

 

Contrariwise, mortar armed vehicles have been considered much more favorably in recent times, due to the appearance of precision guided munitions and infantry carried laser designators.  Top attack is much easier than through the sides, where protection is heavier, and a mortar is cheaper than something like the Bofors Bill missile.

 

The last line, more like 3 inch guns :)  Not so sure of the Russians being a step ahead, it's more like they needed the bigger calibre since their 76.2mm guns were inadequate for their requirements (they would have needed to make their 76's longer and rebalance them for the tanks), and the 85mm had been in production for the SU-85 anyway (since the idea of casemate vehicles, in Russian thinking, was that they carried a bigger gun than the equivalent tank.  Which is why the SU-85 became the SU-100 when the T-34 became the T-34-85).  Instead of re-tooling and re-organising things for a different gun, they went with the logistically more logical choice of the more powerful existing gun when it became feasible to up-arm (since it required a completely different turret, as well as other changes).  The Brits and the US were thinking of bigger guns (the 32 pounder (94mm) (later the 20 pounder (84mm)) and the 90mm), but these required larger vehicles than what was available, and that didn't fit very well with their logistics, since things had to be delivered by existing infrastructure in the ports (which was pretty much maxed out by the M4 Sherman), a restriction the USSR didn't have, since it didn't have to cross any large stretches of water.



Blue_Light #26 Posted Apr 18 2018 - 04:07

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Of course my IS gets killed by one of the little bastards just now since he could do enough damage in that ridiculously short recycle to kill me before I could a second shot off. such bullsh!t.

ColonelHeinzGuderian #27 Posted Apr 18 2018 - 04:11

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View PostBillT, on Apr 16 2018 - 10:00, said:

 

Summarizing what others have said  and expanding a bit:

 

The 57mm gun penetrates well because it has a longer barrel, and that's because it's a smaller diameter than a 75mm.  For the same weight, you can make the barrel longer, and weight is the big problem.  Longer barrel = higher muzzle velocity, and velocity is the biggest factor in armor penetration (and accuracy).

 

Same for the ammunition. The 57mm round is smaller than the 75mm round, so it's easy to  make the cartridge a little longer so you can put even more propellant in it and generate higher pressures in the barrel for even more velocity.  But the small diameter still lets you store more ammunition in your ammo racks or autoloader drums, and because the round is lighter it's quicker to move and load -- faster reload times (whether manual or autoloading).

 

The cost of this is that you can't put very much HE filler in a 57mm round, compared to a 75mm round.  So if you have to shoot at soft targets like infantry or antitank guns, the 57mm is nearly worthless.   That's why the Soviets  didn't put their excellent 57mm in the T34, and why the US waited so long to replace the Sherman's 75mm gun with a longer 76mm (which fired at high velocity, so the shell's sidewalls had to be thicker, so it carried less HE than the 75mm).  In WWII, a tank's main job was to fight infantry. 

 

Also, even the  armor piercing rounds in WWII usually had an explosive filler, a small bursting charge designed to explode inside the target (after penetration).  Rounds smaller than 75mm carried little to no bursting charge, so even if they penetrated they were less likely to destroy the tank.  WOT reflects this in the shell's alpha damage.

 

Thank you.  I haven't fact checked a thing you wrote, but it all makes very good sense to me.  




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