What is the rifle?
Measured the diameter of the trunk-at the beginning of the trunk 13.8 mm, at the end of the trunk at the front sight 12.2 mm. No rifling in the barrel.
It's strange. I don't know what it is but it has a number of hallmarks of a cheap, crudely-made gun, such as the toolmarks left on the breach block. The tapered barrel is a bit of a mystery though. It's usually a feature of an expensive, well-crafted airgun, not a cheapie? It also has a metal buttplate, which cheaper guns tend not to have, unless this one was fitted later - it doesn't seem to fit very well. The screw-on trigger block is certainly not the cheapest way to solve the spring retention problem either.