Is that a vestige of Shelhamer's "chin strap" behind the pistol grip? Hard to tell. The dominating cheek piece is a bit off-putting though, but does tickle my memory of someone's work but I can't put my finger on it. I'll guess too that someone added the stipling around the checkering (and the punch marks), and the horn tip looks like a replacement/after thought (I think I see traces of tearout in the walnut where it was cut for the tip plus the tip doesn't look flush with the walnut in a couple places). I could be seeing things, though.
Could it be a rifle that was simply re-barreled by Niedners?