Hi there Tolley, the rifle in question is a model 44B Heym single shot in 7x57 calibre (7mm Mauser). I think you mistook the calibre for the make of weapon!
The Heym is a beautiful little rifle, very light and extrmely well made. I was a tad dubious as to how it would cope in a fairly large calibre, but the round is a very soft one and even with a 175 grain bullet poses no problems. I am however looking to try some lighter rounds, hence my query. Sorry I couldn't be more help. Good luck