Welcome to Nitro Express!
The 22HP is one of those greats ahead of it's time and I am glad to hear your reloading is going well.
My impression is that the 22HP was quite popular in India as a light buck rifle but has also had enough zoot to take bigger game as well if needed.
I am not sure of the Manton records but I too am interested in looking up another Manton 22HP.