Thanks for that simplified explanation; I have no experience with these sights, so this is appreciated. The original rear sight on my DA Socom is completely useless; inconsistent, unrepeatable and sometimes totally unmoveable. I've toyed with the idea of upgrading it, but it took the combination of this thread, that video and the EE WTS ad for National Match replacement sights to light a fire under my butt. I now have a new sight incoming.
Due to the shorter sight radius on my shortie M14 clone I assume that the clicks won't work as perfectly for 100, 200, etc. but I hope that I can get acceptable results. Any idea if I will need to change the front sight, or will the standard one work well enough?
Standard front sight will be fine but the front sight post MAY be too high (don't stress see below)
The barrel is only shorter by around 3" or so.
I wouldn't think that would throw out the balistics all that far. It's battle accuracy we're talking about here not tack driving precision. More important that you use a cartridge that is close to the original 7.62 Nato ball round ie 147gr FMJ.
This is what you do. Install your new rear sight. Get the ammunition you are going to use predominantly.
Norinco surplus 7.62mm is pretty much bang on what your M14 was designed to shoot and will be calibrated to the dial very closely. There's also MFS 147gr FMJ around for cheap in bulk.
Put your rear sight at exactly 10 clicks up from bottomed out. Disregard the distance notches on the dial for now.
Shoot a 3 round group at exactly 100 meters. You will most likely be hitting the ground in front of the target but I've seen some Norcs that were actually not too far off.
If you are way low take a small flat file and file the front post down until you are bang on at 100 meters for elevation! Be sure to match the angle and keep it square at the rear of the front post. A little at a time. You can take metal away easy but adding it back is a #####! lol
Once you are POA to POI, then you need to unscrew the screw in the elevation dial to disengage the trunion inside from the aperture. Turn the dial so that the first hash mark (the one that has no numbers and is just under the "200" mark) is in line with the notch on rear sight assembly.
Make sure when you do this that your aperture is NOT moving. If it is then back the screw out more. Once it's lined up then hold the dial firm in that spot and tighten the screw down.
You're now calibrated!

Once you get good at the simple math you will be amazed at how efficient you are with the rifle. Of all the guns I've fired and owned over the years, I'm the best and have the most confidence in my M14 by far.
Test it out. It's amazing how well it works.
I would buy a crate of Norc Ammo 7.62mm It's about the closest thing I've found available in cheap bulk to the old school C21 FN FAL rounds/M59 US M14 Cartridges.
Let me know if you need any more help. Will be glad to guide you through anything.