Hi This example of KEnergy and resistance seems incorrect. Sabot. An artillery projectile with narrow core and wide plastic rings to give energy to smaller drag . .. "This, in combination with the sub-projectiles’ higher sectional density, gives the resulting sub-projectile vastly reduced aerodynamic drag in comparison to the APCR. Both the higher initial velocity and the reduced drag result in high velocity at impact." For concrete "The penetration depth increases almost linearly with impact velocity in that range . " Ian V Hogg - 2013 - "This was the Röchling anti-concrete shell (Rö-Geschoss), ... passing through 3m of earth cover, 36m of concrete, a layer of broken stone, gun casement and 5m into the earth .." ---------- Resistance drag in air in given conditions is Area. Velocity sq. A modern sabot is about 5 /18 for core / calibre, core A is 7.5%. As KEnergy is ~ .5 M Vsq then the Area being the size of Mass the velocity sq is the inverse at 1300% . So the sq`/ 13 gives 3.6 times increased Velocity matching the reduced Area giving same drag. Artillery shells penetrate around .6 m into concrete with solid resistance as ~ *. Mass . Velocity. Area. Penetration rises by about .6 with triple the velocity so raising velocity by 3.6 should double penetration to 1m. 7.5% Area should give 13m. penetration but the advantage of 7.5% Mass in the gun is the same disadvantage in concrete . How then did the Germans penetrate 36m concrete + 8m earth?