A customer of mine has a simular rifle by Ferlac chambered for 6.5X57. Your best bet would be to do a chamber cast and find the case dementions. The book Cartridge Conversions would help you out in tracking down just what the chambering is. If you get stuck send me the demsions and I may be able to help you out. P.S., you ant to get rid of that reciever sight????