According to Livingston & Bird (Which base their figures on German, US & British tests) the performance of the 7.5cm KwK40 L/43 & L/48 is as follows:
7.5cm KwK40 L/43
Muzzle velocity: 740 m/s (Pzgr.39), 920 m/s (Pzgr.40)
Penetration performance against 240 BHN RHA armour at right impact angles (0/90 degree’s)
100m = 133mm (Pzgr.39), 173mm (Pzgr.40)
500m = 121mm (Pzgr.39), 151mm (Pzgr.40)
1,000m = 107mm (Pzgr.39), 127mm (Pzgr.40)
1,500m = 95mm (Pzgr.39), 108mm (Pzgr.40)
2,000m = 85mm (Pzgr.39), 91mm (Pzgr.40)
2,500m = 75mm (Pzgr.39), 77mm (Pzgr.40)
7.5cm KwK40 L/48
Muzzle velocity: 750 m/s (Pzgr.39), 930 m/s (Pzgr.40)
Penetration performance against 240 BHN RHA armour at right impact angles (0/90 degree’s)
100m = 135mm (Pzgr.39), 176mm (Pzgr.40)
500m = 123mm (Pzgr.39), 154mm (Pzgr.40)
1,000m = 109mm (Pzgr.39), 130mm (Pzgr.40)
1,500m = 97mm (Pzgr.39), 109mm (Pzgr.40)
2,000m = 86mm (Pzgr.39), 92mm (Pzgr.40)
2,500m = 76mm (Pzgr.39), 78mm (Pzgr.40)
7.5cm PaK40 L/46
Muzzle velocity: 792 m/s (Pzgr.39), 990 m/s (Pzgr.40)
Penetration performance against 240 BHN RHA armour at right impact angles (0/90 degree’s)
100m = 146mm (Pzgr.39), 195mm (Pzgr.40)
500m = 133mm (Pzgr.39), 170mm (Pzgr.40)
1,000m = 118mm (Pzgr.39), 144mm (Pzgr.40)
1,500m = 105mm (Pzgr.39), 121mm (Pzgr.40)
2,000m = 93mm (Pzgr.39), 102mm (Pzgr.40)
2,500m = 82mm (Pzge.39), 86mm (Pzgr.40)
the results doesnt seem much different and tbh im not much of tank nerd the topic suggest due to rifling / ease of manufacturing / what ever reason is why they chose to go with L48 instead of L43
https://forum.axishistory.com/viewtopic.php?t=138243