95% probability limit is x1.645 times the SD, so if we take SD of ballistic limit to be 50fps, the velocity where 95% of shots will defeat the armour is 82fps higher than 50% limit used by the US.
We can use the relationship of Penetration vs Velocity from DeMarre formula to calculate how much this change in limit velocity alters the thickness defeated:
Striking Velocity (fps):
50% penetration thickness (reference):
95% penetration thickness:
5% penetration thickness:
1500
100
93
108
1600
100
93
108
1700
100
93
107
1800
100
94
107
1900
100
94
107
2000
100
94
106
2100
100
95
106
2200
100
95
106
2300
100
95
105
2400
100
95
105
2500
100
95
105
2600
100
96
105
2700
100
96
105
2800
100
96
104
2900
100
96
104
3000
100
96
104
This information can be used in following way: if, let's say, the US 75mm M61 APC round will perforate, with projectile going all the way through, the Tiger I's side armour with 50% probability at exactly 500m, that's the s.v. of 1858fps, which means that it will defeat it on 95% shots at s.v. 82fps higher or 1940fps which is 250m.