wwI

This is one of the first dedicated anti tank guns - the Mauser 1918 TuF (tank und fleiger)

While it weighed 41 pounds with bipod attached, the bullet weighed nearly two ounces & left the muzzle at about 2800 feet per second. Recoil was horrendous! It could do damage though - it could penetrate almost an inch of period armor at 100 meters... if the shooter could stand to fire it.

https://en.wikipedia.org/wiki/Mauser_1918_T-Gewehr

I suppose even if it didnt penetrate fully it would create some deadly Spall inside the tank?

I believe so given the use of cast iron and riveted construction. We also see evidence of spall danger in the chain protection worn by early British tank crews.

Overall, though the most pain was felt by the unlucky soul who was expected to fire this beast accurately. I would want no part of it!

Found these pics of splinter protection. Heavy leather coats were regular kit for some units, but they weren't always worn.