"Gents; I have read that the 7x53R is made for ptarmigan shooting and the barrels were rifled with slow twists {+- 1 in 14 or so} and thus not good for shooting heavy bullets for hirvi, etc. Can you verify that?"

That't true. I have one 7x53R custom -Mosin made by Aarre Viitanen, Kauhajoki in early 1960's. I have done it little bit more so original look was nearly same as the upper rifle.

I have noticed that 155 grain bullet is the heaviest one which you can use with my barrel.