My source Waffen und Geheimwaffen des deutschen Heeres 1933-1945 by Fritz Hahn, apparently has too low figures for the 7,5-cm-KwK 37 L/24 HEAT performance: According to Datenblätter für Heeres-Waffen, -Fahrzeuge und -Gerät the penetration of 7,5 cm Gr.38 Hl/C was 90 mm at all ranges so the L/24 was distinctly superior to the PzGr 40-less Pak 38 at all ranges in armour penetration also.peeved wrote:Hohlladungsgranate 38 C of the 7,5-cm-KwK 37/L/24 pierced 75 mm of armour at all distances which the 5-cm-PzGr 39 from a Pak 38 only matched at point blank ranges (as usual German penetration figures being given at an 60 deg. angle of impact).
In fact the rifling length of an imaginary Pak 50 with Pak 40 chamber would be only ca. 40% of the Pak 40 rifling length 1719mm - 716 mm (Pak 40 chamber length) = 1003 mm vs. 2461 mm. One can approximate the effect of this amputation from the formula way below from Rheinmetall's Waffentechnisches Taschenbuch. xe being rifling length, mp projectile weight, mc propellant charge weight, ve muzzle velocity, A cross-sectional area of the bore, ηp pressure relation and pm maximum gas pressure in bore. Using known values for the Pak 40: xe 2,461 m, mp 6,8 kg, mc 2,77 kg, ve 792 m/s, A ca. 0,805 x 0,075^2 m^2 and pm 2800 x 10^5 N/m^2 (2800 bar) the ηp would yield 0,822718 which with a rifling length of 1,003 m would yield ca. 505 m/s of muzzle velocity. The actual muzzle velocity as given by the formula for the imaginary Pak 40/50 would be somewhat higher since ηp is calculated from: mean pressure / max pressure and mean pressure would be higher in a shortened tube. It is still hard to believe that the Germans would have gone through all the trouble to lose that much muzzle velocity, i.e. making the Pak 40 punier than a Pak 97/38, and to produce a lot more telltale sound and fury with the increased muzzle blast. Sort of contradicts such previous statements as:The Pak 40 chop shop theory is based on little sense although it would have been a blast... Muzzle blast; merely wasting ballistical potential in a barrel about half the length of the one intended by the Pak 40 designers.
andAlanmccoubrey wrote:The Pak 50 as described by this WR 102 is a compleytely illogical waste of effort while the Pak 50 as described in Hogg's Artillery book and Lexikon der Wehrmacht is at least based on a bit of sense.
Spontoon: I'm pretty sure the Pak 50s were bored out Pak 38s. The German documents consistently use the verb ausbohren, bore out in the context of Pak 50; the reboring was just my slightly inaccurate translation. Reboring just seemed to me the more usual term although technically it could also include relining.The idea of the Pak 50 was supposedly to provide a lighter gun with a similar a/t performance tro the Pak 40
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