BCBoy,
Sorry about the sight, it is really a piece of shit. In perfect condition the originals are selling for $185, some repos are selling for $125. So keep it or get a good buck when you sell it. I bought a perfect original for $175, but sold it for $185 after I deceded it was very poorly designed and manufactured.
Yes, you need to loosen one screw and then adjust the other. The elevation is even less quality, if moves easily when you don't want it.
No one makes a better M71 bolt sight, but you could get a ghost sight for a pistol and drill and tap for it. Not a thing of beauty, but it would work.
If you have an original M71, it will not be drilled nor tapped for receiver sight or scope. If it is tapped, it was done after purchase. Drilling and tapping an original in perfect shape will take about $400 of the gun's value. Your choice. If it was tapped a good Lyman receiver sight is the way to go. I leave the aperature out of the sight and it is like a ghost sight. that is where the 'ghost sight' came from. I'd also get a front firesight.
I've got to run, talk later
BEAR