Meyer Optik Telemegor 300mm f4.5 on Nikon - Infinity Focus

[doyourhomework]

I recently purchased a Meyer Optik Telemegor 300mm f4.5 in Pentacon Six mount. With a Nikon adapter (P6 to Nikon F), I cannot achieve anywhere near infinity focus. I find this odd as the mount has a flange focal distance far greater than that of the Nikon. I did a bit of unscientific testing and what is roughly 10 feet in real world distance is at about 25 feet on the scale of the lens. Any ideas? The lens is in great shape and seems to have been well cared for. Thanks for any help!