Lots of guys have put 77/22 barrels on a 10/22, including me. My main reason is that I could get a 77 barrel that wasn't available for the 10/22. Also, GM frequently has barrels on killer deals for one platform or the other. There's a lot of motivation to put a 77/22 barrel on a 10/22 when the barrel only cost $35.Right and I see no reason to put a 10/22 barrel on a 77. Actually it's just better to get the right barrel for your gun.
The half moon piece (nub) doesn't help barrel droop. It's purpose is to rotate the barrel slightly since the 77/22 extractor slot is cut in a slightly different location than the 10/22.Q: Finally, does the small metal nub adjust barrel droop?
Q: If so, I can also fix this (or may also need to fix this) with an adjustable v-block if I run out of adjustment on my scope, right?