[Warhorse]

I have a 1/7" AR-A2 with a 20" barrel. I mounted my 2X7 compact scope to the carry handle with a no brand, 20 year old mount that has a thumb wheel for tightening it to the handle. While shooting 20 rounds to zero the scope, the wheel loosens up.
Would a lock washer help keep it tight enough?

Is there another type mount that would work better?

I am loading 75grn Hornady match bullets for 100 and 200 yard targets.

[Constructor]

Kind of depends on what the threads look like after 20 years but a lock washer could help, a nyloc nut would also work. They make a reusable loctite too, purple I think.
With only one lock down it will never hold as tight as a set of good tactical rings but some times you just have to work with what you have.