According to Hunnicutt: "Halftrack....", the 75mm M1987A4 managed
APC M61
500 yards: 64mm
1000 yards: 58mm
1500 yards: 52mm
2000 yards: 48mm
AP M72
500 yards: 74mm
1000 yards: 61mm
1500 yards: 48mm
2000 yards: 38mm
all vs homogenous armour at 30 degrees.
Figures for the 7,5cm PaK 97/38 from varous German books suggest
Polish AP? (armour type and angle unknown)
500m: 58mm
Polish AP? (armour type and angle unknown)
100m: 61mm
1000m: 58mm
Seems pretty much in the same ballpark to me. The US M72 round was an uncapped monobloc rounds with no HE filler and would probably be a bit more robust during penetration than rounds with an HE filler. The M61 was a capped round with HE filler. No idea about the Polish one.
David Lehmann, who usually have his sources in order quotes the following for french AP ammunition fired from the 75mm L/34.5 Mle1897/33
Obus de rupture Mle1910M (AP/HE) (0 degree impact, armour type unknown)
100m: 71.5mm
500m: 61.5mm
Obus perforant AL (Allongé Lefèvre) Mle 1916 (AP/HE) (30 degrees, armour type unknown)
400m: 40mm
Obus perforant AL (Allongé Lefèvre) Mle 1918 (AP/HE)(30 degrees, armour type unknown)
400m: 40mm
A usual, different testing conditions and criteria may apply and could screw up any meaningfull comparison
cbo