Sure it does; "overmatching" is what you get when the thickness of the armor (T) is less than the diameter of the AP round (D). If T/D is less than 1, then you have overmatch. If T/D drops below 1 it tends to reduce the effects of sloping armor. T/D works both ways; if it raises above 1, then the effects of slope is increased, particularly against high angles. That is why the T-34's amour was quite effective against the most common threats it faced around the time it was introduced to combat. Those threats were 20 mm - 50 mm guns, which the T-34s sloped 45mm hull amour dealt with quite well.
Cut and paste time:
"Armor obliquity effects decrease as the shot diameter overmatches plate thickness in part because there is a smaller cylindrical surface area of the displaced slug of armor which can cling to the surrounding plate. If the volume which the shot displaces has lots of area to cling to the parent plate, it resists penetration better than if that same volume is spread out into a disc with relatively small area where it joins the undisturbed armor. Plate greatly overmatching shot involves the projectile digging its own tunnel, as it were, through the thick interior of the plate. It was found experimentally that the regions in the center of the plate produced the bulk of the resistance to penetration, while the outer regions, near front and rear surfaces, presented minimal resistance because they are unsupported. Thus, an overmatched plate will be forced to rely on tensile stresses within the displaced disc, and will tend to break out in front of the attacking projectile, regardless of whether the edges cling to the parent material or not. Plate obliquity works in defeating projectiles partly because it turns and deflects the projectile before it begins digging in. If there is insufficient material where the side of the nose contacts the plate, stresses will travel all the way through the plate and break out the unsupported back surface. The plate will fail instantaneously rather than gradually.
You can angle the armor any way you want, and beyond a certain point of shot overmatching plate, the obliquity will cease to be relevant. In fact, at certain conditions of shot overmatching plate, the cosine rule is broken and the plate resists less well than the simple cosine relationship would predict (LOS thickness is greater than effective thickness). The above only applies to WWII era AP and APC/APCBC, and WWII sub caliber ammunition. The long rod penetrators of today are greatly overmatched but they bring so much energy to the plate that they penetrate by "ablation" in which both projectile and armor behave like fluids. Hollow charge also enters the field of fluid dynamics, with a very thin jet penetrating overmatching armor with ease, regardless of obliquity"
In this hypothetical confrontation we have a 75 mm shell vs. 51 mm target plate angeled at 34 degrees from horizontal giving a theoretical effective thickness of 91 mm. However, if we take round overmatching into account the effective armor would be:
armor thickness*(1+((slope multiplier -1)*overmatch factor))
Armor = 51 mm
Shell = 75 mm
Slope = 34 degrees from horizontal
Slope multiplier = 1.7
Overmatch factor (T/D) = 0.6
51*(1+((1.7-1)*0.6))= 72 mm effective thickness against a 75 mm shell.
Against this effective armor we must use penetration data calibrated for 0 degrees of slope (slope is already factored in the effective armor thickness). At 500 yards: 91 mm - 1,000 yards: 75 mm - 1,500 yards: 61 mm.
Even if we don't factor in the reduction of effective slope by the ballistic trajectory of the incoming shell the results are pretty clear, so my previous conclusion stands: A 75 mm armed M4 would be able to penetrate the 51 mm glacis plate of another M4 at more than 1,000 yards. At 1,500 yards penetration would be possible under favorable conditions. At 2,000 yards penetration would be unlikely except for lucky hits on weak spots.
