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  • 4 weeks later...

What allowed the 105mm M68 to be so compact compared to the D-10T? was it primarily in the design of the Concentric recoil system or was the steel used in the M68 stronger to allow it to be lighter, and if the difference was in the steel alloys used what were they, trying to use google to find information on tank gun design and the steels used and trying to find patents of M68 and others seems fruitless.

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2 hours ago, Toimisto said:

What allowed the 105mm M68 to be so compact compared to the D-10T? was it primarily in the design of the Concentric recoil system or was the steel used in the M68 stronger to allow it to be lighter, and if the difference was in the steel alloys used what were they, trying to use google to find information on tank gun design and the steels used and trying to find patents of M68 and others seems fruitless.

 

I'm going off the top of my head, don't have references handy at the moment, but it's basically a function of breech pressure limit.  I'm not sure what it is about the design of the M68 that allowed it to have a higher limit than the D-10; better metallurgy, or just a slimmer safety margin or what.  But the short version is that you can get the same performance out of a smaller propelling charge and smaller gun if you run the pressures higher.

There's a thread here comparing the L7 and D-10 by the straightforward method of comparing projectile kinetic energy that concludes that the D-10 is actually more powerful than the L7.  But this is incorrect.  The highest kinetic energy projectiles the D-10 fires are full caliber AP projectiles, and the L7 does not fire full caliber AP projectiles.  Kinetic energy figures are only comparable if the projectiles being compared are of similar muzzle velocity, because there is an efficiency parameter that is a function of velocity.  I haven't done an exhaustive look at figures, but from what I recall L7 APFSDS is more powerful than D-10 APFSDS.  If the L7 fired full caliber steel AP, it would probably beat the D-10.

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  • 2 weeks later...
14 hours ago, Khand-e said:

 

You forgot the STAFF.

 

.....5th times a charm maybe possibly?

 

I was going to argue that it doesn't really count because it's a completely different type of round, but MRM-CE isn't a rocket boosted kinetic penetrator either.

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On 18.9.2016 at 8:22 PM, Militarysta said:

Hi Methos,

to be onest - In article I had used two russian sources :-) couse they have the same metodology:

 

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Of course some of them was estimatous.

 

In term this polish military press - no hard data, just form context - couse diffrent gun.

 

btw: DU vs WHA it's old story,  in some sources there is 18% difrences between both material...

can anyone please provide sources for this data? I would need it :D That would be great

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  • 2 weeks later...

Does someone have documents relating to the decrease of efficiency of bottlenecked ammunition compared to straight walled, and the effects of case taper, trying to figure out how much a  smaller bore straight walled case is inferior to a straight walled larger bore case if both have the same  cartridge base diameter, especially when concerning their efficiency in pushing APDS. 

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8 hours ago, Toimisto said:

Does someone have documents relating to the decrease of efficiency of bottlenecked ammunition compared to straight walled, and the effects of case taper, trying to figure out how much a  smaller bore straight walled case is inferior to a straight walled larger bore case if both have the same  cartridge base diameter, especially when concerning their efficiency in pushing APDS. 

 

If you're keeping the barrel length constant, then a bottlenecked case loses swept volume (and you can use the work done by adiabatic expansion over that pdV integral for a rough approximation of the difference in efficiency). Case taper loses case volume, AFAIK any difference in the resistance to flow between different case geometries is not very significant

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1 hour ago, Karamazov said:

Can somebody tell me about rifled tank guns? What is the accuracy in comparison with smooth-bore guns? For example Challenger 2 L30E4 and Leopard 2 Rh120 L55

I don't have any numbers, but the general rule of thumb is that when you use fin stabilized ammunition, you're going to get better accuracy from smoothbore guns than you would from rifled guns. 

So that means APFSDS, HEAT-MP, HE-MP, and practically anything that isn't HESH. And HESH loses out to HE-MP in every parameter.

 

Basically you want to use smoothbore guns.

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11 hours ago, Xlucine said:

 

If you're keeping the barrel length constant, then a bottlenecked case loses swept volume (and you can use the work done by adiabatic expansion over that pdV integral for a rough approximation of the difference in efficiency). Case taper loses case volume, AFAIK any difference in the resistance to flow between different case geometries is not very significant

 

I've seen some papers on the constriction of the bottleneck leading to better combustion in small arms, but I don't know if this effect still exists in larger weapons.  The effect was, in any case, small.

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7 hours ago, Karamazov said:

Can somebody tell me about rifled tank guns? What is the accuracy in comparison with smooth-bore guns? For example Challenger 2 L30E4 and Leopard 2 Rh120 L55

 

If we are talking fin stabilized ammunition, then any meaningful differences should be a product of the specific gun, ammunition and fire control system than whether the gun is rifled or smoothbore.

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42 minutes ago, Ramlaen said:

 

If we are talking fin stabilized ammunition, then any meaningful differences should be a product of the specific gun, ammunition and fire control system than whether the gun is rifled or smoothbore.

 

I agree.  Fin-stabilized ammunition fired out of rifled guns has slip rings to keep the projectile from spinning.  A rifled gun firing anything with fins is very close to smoothbore.

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1 hour ago, Collimatrix said:

 

I agree.  Fin-stabilized ammunition fired out of rifled guns has slip rings to keep the projectile from spinning.  A rifled gun firing anything with fins is very close to smoothbore.

Slip rings may negate the loss of accuracy, but they take away some of the initial velocity which is also bad. 

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11 hours ago, Collimatrix said:

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That seems to be a rather superficial statement. What is a "standard charge weight" and how heavy is the projectile? Mathematically the 120 mm DM43 should reach 1,800 m/s when fired from the L/55 gun (muzzle velocity from L/44: 1,740 m/s, muzzle velocity from L/52: 1,780 m/s).

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