US 76mm vs 17pdr vs 7.5cm KwK42 L/70

Gordon

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Does anyone know of good reference materials that discuss the above referenced guns and explains the performance differences between them? Was it simply the difference in calibers? Propellant weight/efficiency? Metallurgical differences? Other differences?

TIA
 

Michael Dorosh

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Does anyone know of good reference materials that discuss the above referenced guns and explains the performance differences between them? Was it simply the difference in calibers? Propellant weight/efficiency? Metallurgical differences? Other differences?

TIA
I would think muzzle velocity plays a part, off the top of my head.

14674
 

The Purist

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The German L/48 and US L/52 had roughly similar performance characteristics mainly due to the propellent and barrel length

The 17 pdr, despite being the equivalent of L/55, had a much larger propellent charge and the length of barrel and breach depth/strength to support the muzzle velocity. It was the propellent that made the British 17 pdr and German 75 L/70 on the Pz V roughly equal in performance. With APDS the penetration of the 17 pdr was even more potent (as we see in the game)
 

Actionjick

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The German L/48 and US L/52 had roughly similar performance characteristics mainly due to the propellent and barrel length

The 17 pdr, despite being the equivalent of L/55, had a much larger propellent charge and the length of barrel and breach to support the muzzle velocity. It was the propellent that made the British 17 pdr and German 75 L/70 on the Pz V roughly equal in performance. With APDS the penetration of the 17 pdr was even more potent (as we see in the game)
I got nothing. Cat nudged my arm as I was scrolling and hit reply. She must have an opinion but hasn't told me yet.
 

RandyT0001

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Barrel length is important to the gun's effectiveness. A longer barrel allows the charge to push the shell out the muzzle faster (up to a point when friction starts to counter it, typically longer than either barrel in question, IIRC).
 

Eagle4ty

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The German L/48 and US L/52 had roughly similar performance characteristics mainly due to the propellant and barrel length

The 17 pdr, despite being the equivalent of L/55, had a much larger propellant charge and the length of barrel and breach depth/strength to support the muzzle velocity. It was the propellant that made the British 17 pdr and German 75 L/70 on the Pz V roughly equal in performance. With APDS the penetration of the 17 pdr was even more potent (as we see in the game)
Implied by your response of course is the reason APDS had such an increased muzzle velocity and thus increased inertial force of it penetrator. As noted barrel length allowed much more of a propellant to be utilized (and/or a greater explosive propellant to be used) in forcing the projectile down the barrel increasing muzzle velocity and was only slightly offset by the drag induced by the right hand grooves in the barrel (rifling). However this only accounted for a few hundred m/s or ft/s increase a round's muzzle velocity and thus its increase of penetration potential. However, the SABOT penetrator of an APDS leaves it to be propelled by the charge to a much greater degree as the breakaway outer sleeve absorbs much of the drag induced by the rifling without impacting the actual penetrator to any significant degree. The only real drawbacks of using APDS was sighting differences as the projectile had much less of a right hand drift (almost none) induced by the rifling common to AP, APCBC, and other usual rounds, and the fact that for engagements at greater than it listed effective range the inertial energy of the penetrator dropped off significantly compared to its "rifled" counterparts.
 

von Marwitz

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Barrel length is important to the gun's effectiveness. A longer barrel allows the charge to push the shell out the muzzle faster (up to a point when friction starts to counter it, typically longer than either barrel in question, IIRC).
This is correct.

But at a certain point, other considerations also come into play: If the barrel gets too long, precision is inhibited by vibrations and the slight bending of the barrel. I am not a gun-guru but remember reading about the Germans experimenting with some longer barrels for tanks and assault guns and then ran into these problems.

von Marwitz
 

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Does anyone know of good reference materials that discuss the above referenced guns and explains the performance differences between them? Was it simply the difference in calibers? Propellant weight/efficiency? Metallurgical differences? Other differences?

TIA
It is indeed mostly due to muzzle velocity. When you look at a gun it generally has a second number: 75/40. The second number is the length of the gun measured in gun calibers: e.g. 3000mm or 3m. The longer the barrel, the higher the muzzle velocity. However, you also have to consider metallurgy. Soviet metallurgy was notoriously bad and German metallurgy deteriorated toward the end of the war due to the loss of access to nickle and other raw materials needed to harden steel (which should, but does not, affect armor factors.)

Consider also muzzle brakes. Muzzle brakes redirect propellant gases and allow the installation of larger guns on the same size turret. The British 17lbr was the absolute max that you could install on a Sherman turret, allowed by the use of the muzzle brake.

Finally, some guns used squeeze bore principles to increase muzzle velocity. The German 28mm anti-tank rifle actually had a 20mm penetrator with a mesh which squeezed down to 20mm by the time it is released from the bore, increasing muzzle velocity and hence, penetration. However, such high velocity for a small penetrator led to the shattering of the projectile when it hit, so special manufacturing using nickle projectiles had to be created.
 

T34

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This is correct.

But at a certain point, other considerations also come into play: If the barrel gets too long, precision is inhibited by vibrations and the slight bending of the barrel. I am not a gun-guru but remember reading about the Germans experimenting with some longer barrels for tanks and assault guns and then ran into these problems.

von Marwitz
Also, the higher the velocity, the greater the barrel wear. So militaries are reluctant to produce guns that have to have their barrel replaced on too short a time.
 

The Purist

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... <snip>...The only real drawbacks of using APDS was sighting differences as the projectile had much less of a right hand drift (almost none) induced by the rifling common to AP, APCBC, and other usual rounds, and the fact that for engagements at greater than it listed effective range the inertial energy of the penetrator dropped off significantly compared to its "rifled" counterparts.
The problem with the early APDS was that they were spin stabilized, which led to a drop off in accuracy as the range increased. When APFSDS came along (AP Fin Stabilized DS) accuracy was greatly improved.

(Learneded dat in da tank schule in Gagetown back in my army tank days.... yup, they let me ride around in their tanks and shoot the big gun)

(Erm,... Gagetown is an army base in Canada, the eastern coast bit,.... in a province known as New Brunswick).
 

The Purist

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This is correct.

But at a certain point, other considerations also come into play: If the barrel gets too long, precision is inhibited by vibrations and the slight bending of the barrel. I am not a gun-guru but remember reading about the Germans experimenting with some longer barrels for tanks and assault guns and then ran into these problems.

von Marwitz
Back in the day we were schooled on how air temperature, wind and barrel temperature from earlier shots could all effect long range shooting. "Barrel Bend", even from a stiff wind, could cause a miss. This was more often the case with "stab off" but even with stabilization and laser range finders, combined with vehicle motion, a shot could (just) miss due to barrel bend.

Talking here about the NATO 105mm L7 rifled tank gun.
 
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