how can i best bend/curve a mesh or fix this glitchy looking bend? i have an imported model of a tank/mech with a tank barrel on it, im planning to use this model for posing purposes, in the program it exports from i can rotate the turret and pose it in many ways however in blender i need to bent the turret backward on itself like seen in superhero movies or in movies where a gun barrel is bent. 

i have tried using, bevel tool (doesnt work), the deform tool (doesnt work), and the curve modifier (partly works but glitches) wherever the vertex group mesh section connects to a non curved part of the mesh there is a straight then sudden 90 degree glitchy looking turn  i dont know how to fix this issue as any selecting just moves the next part of the mesh as the glitched turn.
Using a curve modifier and starting from this position (curve modifier on the canon) :




Go to edit mode
ctrl+R, the move to the straight cylinder part and mouse wheel or use page up to increase the number of cuts 
Validate using LMB, eventually move the cuts, then LMB again (or escape to stay at the initial position)