Notes:

I actually survived this, the whole video can be found here.

Quick review of the S-51:

Misses 90% of it's shots, so HE is preferred unless you're playing it as a defensive tank destroyer, which it's surprisingly good at, then go with AP.

Hitting a tier V Sherman with an 203mm AP round is very satisfying, as is one-shotting everything apart from the Mini-Maus and the Type-4 Heavy.