Hey,
I have an original Danish M1D as well. Springfield Jan 1943 reciever, June 1952 Barrel. All in overall Excellent+ condition. I searched high and low for information on the sniper's so that I could really learn about it and more importantly, the M84 scope. I finally found what everyone that has either an M1D, MC1 or M1C needs to know. It is found ONLY in the 1958 version of FM-23-5. I happened to find an original on ebay a year or so ago. Supposedly from a US Veteran from Vietnam! Anyway, go to the following site and you can download it for free!!! Along with almost all of the other previous and post copies of FM-23-5, and tons of manuals for most of the other US military weapons, tactics, information and other stuff!!! Ever wondered how to work that WWll flamethrower that you have in your basement??? Remove the space in the www and you are there! The first 44 pages are full of official edits an revisions. It actually starts on page 46. The section that you need to read for the sniper rifle (Specific to the M1C that uses the M84 scope, is in chapter 7 "Sniping" on page 208 in the actual manual or page 253 of the PDF.
w ww.90thidpg.us/Reference/Manuals/index.html
Hope this helps everyone that has one of these awesome rifles, or any other US milsurp for that matter,
Smitsauce