Shipka are you sure there were such cannons in defence of Warsaw in 1831 ?
Most intensive fights - where the lines were breached by Russians was makeshift fortification (Dzieło 56 - Work 56/Redoubt 56) and was served by artillery on field mounts (like on most famous painting of Death of gen Sowiński
(by accident Redoubt is around 800 meters from my flat)
Ive never been to church visible on the picture - which is still standing but i read somewhere that it has some cannon barrels inside.