The weapon was effective against almost every Allied tank until the end of the war, only struggling to penetrate heavier vehicles like the Russian IS tanks, the American M4A3E2 Sherman 'Jumbo' and M26 Pershing, and later variants of the British Churchill tank.
The Pak 40 was much heavier than the Pak 38; its decreased mobility meant that it was difficult or even impossible to move without an artillery tractor on boggy ground.

The Pak 40 was first used in the USSR where it was needed to combat the newest Soviet tanks.
It was designed to fire the same low-capacity APCBC, HE and HL projectiles that had been standardized for use in the long barrelled Kampfwagenkanone KwK 40 tank-mounted guns of the mid-war and later marks of the Panzer IV medium tank.
In addition, there was an APCR shot (Panzergranate 40) for the Pak 40, a munition which - reliant on supplies of tungsten - eventually became very scarce.
According to the German Panzertruppen News Journal, 5,000 APCR rounds were expected in Dec. 1942 as replenishment for the Winter offensive.

The main differences amongst the rounds fired by 75 mm German guns were in the length and shape of the cartridge cases as well as the primers used.
The 7.5 cm KwK 40 (75x495mm) used in tanks had a fixed cartridge case twice the length of that used by the 7.5 cm KwK 37, the short barrelled 75 mm used on earlier tanks, and the 7.5 cm Pak 40 cartridge was a third longer than that used by the KwK 40.
The Pak 40 used a percussion primer, while the vehicle mounted 75 mm guns used electrical primers.
Other than minor differences with the projectiles' driving bands, all German 75 mm guns used the same 75mm projectiles.

The longer cartridge case of the Pak 40 allowed a larger charge to be used and a higher velocity for the PzGr 39 armour-piercing capped ballistic cap round to be achieved.
The muzzle velocity was about 790 m/s (2,600 ft/s) as opposed to 740 m/s (2,400 ft/s) for the KwK 40 L/43 and 750 m/s (2,500 ft/s) for the L/48.
The only 75mm fighting vehicle gun in general use by Germany that possessed a longer barrel than the Pak 40, the 7.5 cm KwK 42 on the Panther tank, could achieve a higher muzzle velocity of 935 m/s (3,070 ft/s) on what was essentially the same calibre and model of shell, with a differing propellant cartridge fixed to it for the KwK 42's use.

For unknown reasons, some 75 mm APCBC cartridges appear to have been produced with a charge that gave a muzzle velocity of about 770 m/s (2,500 ft/s).
The first documented firing by the US of a Pak 40 recorded an average muzzle velocity of 776 m/s for its nine most instrumented firings.
Probably because of these results, period intelligence publications ("Handbook on German Military Forces") gave about 770 m/s as the Pak 40 APCBC muzzle velocity.
Post war publications corrected this.

German sources differ; the Official Firing Table document for the 75 mm KwK 40, StuK 40 and the Pak 40 dated October, 1943, gives 770 m/s on one of the APCBC tables.
The weapon was effective against almost every Allied tank until the end of the war, only struggling to penetrate heavier vehicles like the Russian IS tanks, the American M4A3E2 Sherman 'Jumbo' and M26 Pershing, and later variants of the British Churchill tank. The Pak 40 was much heavier than the Pak 38; its decreased mobility meant that it was difficult or even impossible to move without an artillery tractor on boggy ground.
The Pak 40 was first used in the USSR where it was needed to combat the newest Soviet tanks. It was designed to fire the same low-capacity APCBC, HE and HL projectiles that had been standardized for use in the long barrelled Kampfwagenkanone KwK 40 tank-mounted guns of the mid-war and later marks of the Panzer IV medium tank. In addition, there was an APCR shot (Panzergranate 40) for the Pak 40, a munition which - reliant on supplies of tungsten - eventually became very scarce. According to the German Panzertruppen News Journal, 5,000 APCR rounds were expected in Dec. 1942 as replenishment for the Winter offensive.
The main differences amongst the rounds fired by 75 mm German guns were in the length and shape of the cartridge cases as well as the primers used. The 7.5 cm KwK 40 (75x495mm) used in tanks had a fixed cartridge case twice the length of that used by the 7.5 cm KwK 37, the short barrelled 75 mm used on earlier tanks, and the 7.5 cm Pak 40 cartridge was a third longer than that used by the KwK 40. The Pak 40 used a percussion primer, while the vehicle mounted 75 mm guns used electrical primers. Other than minor differences with the projectiles' driving bands, all German 75 mm guns used the same 75mm projectiles.
The longer cartridge case of the Pak 40 allowed a larger charge to be used and a higher velocity for the PzGr 39 armour-piercing capped ballistic cap round to be achieved. The muzzle velocity was about 790 m/s (2,600 ft/s) as opposed to 740 m/s (2,400 ft/s) for the KwK 40 L/43 and 750 m/s (2,500 ft/s) for the L/48. The only 75mm fighting vehicle gun in general use by Germany that possessed a longer barrel than the Pak 40, the 7.5 cm KwK 42 on the Panther tank, could achieve a higher muzzle velocity of 935 m/s (3,070 ft/s) on what was essentially the same calibre and model of shell, with a differing propellant cartridge fixed to it for the KwK 42's use.
For unknown reasons, some 75 mm APCBC cartridges appear to have been produced with a charge that gave a muzzle velocity of about 770 m/s (2,500 ft/s). The first documented firing by the US of a Pak 40 recorded an average muzzle velocity of 776 m/s for its nine most instrumented firings. Probably because of these results, period intelligence publications ("Handbook on German Military Forces") gave about 770 m/s as the Pak 40 APCBC muzzle velocity. Post war publications corrected this.
German sources differ; the Official Firing Table document for the 75 mm KwK 40, StuK 40 and the Pak 40 dated October, 1943, gives 770 m/s on one of the APCBC tables.
7.5 cm Pak 40