Hi i have a Sauer 404 Synchro XT in 6.5x55, out of box accuracy sub moa, don't think you can get a picatinny rail (maybe wrong ) mine came with a SUM mount its top notch and would not change it, but it's not cheap.
I was really keen on these last year, particularly the Synchro XT with the adjustable comb. When I finally got my hands on one, I was disappointed to find that certainly in larger calibres, getting the bolt out means lowering the comb from where I like it set. It might sound trivial but that was a deal breaker to me and I didn't buy the rifle. Such a shame, it was a joy to hold, great fit, build, buttery smooth action, great trigger, excellent features.
The sight mount price was also a bit eye watering, especially as it's a take down so wanting a different sight was a real possibility.