Eastern Gun pits.
This is about as good as the muzzle loaders got. This is a rifled cannon. Look carefully at the barrel plug and you can see the rifling lands on the tube. The metal mount is now fully fabricated from rolled sections and is no longer jerked about by hand spikes, there is a gear traverse on the driving wheels. Still must have been a bit of a bother to train in the hot sun. The bang end has a large wraparound tube to contain the pop compared to the continuous cast of the older weapons. Not a pretty thing.