Perhaps someone here can help me. I have a very nice Mannlicher Schoenauer Puch Model 50 (I think) in 7x57 Mauser and a second M-S Model MCA in .308 Winchester. The Model 50 has signed factory engraving, a bolt-mounted aperture sight, single trigger, and a very dark conventional- not full length and no Monte Carlo configuration- stock. The .308 has the factory set trigger.
Here are my questions: first and most important, the 7x57 consistently fails to feed the 4th, next to last round, from the rotary/spool magazine. Once I clear that round it feeds the last round perfectly every time. Has anyone experienced similar malfunctions and if so, what's the fix? Secondly, does anyone still make a quick release scope mount for these rifles? The 7x57 has been scoped and the mount works fine except I can't readily detach it to allow me to use the iron sights. Lastly, I'd really like to swap the triggers and put the set trigger on the 7x57. Obviously I'd have a gunsmith do the work but I'd rather not tie up both rifles if the swap is impossible.
Any help anyone can give- especially if they know a gunsmith in the Chicago area that is familiar with Mannlichers- will be greatly appreciated. TIA.

Bob