Either a scope moves and is unacceptable, or it does not move and works properly...I am not sure what you mean by "holding .5 MOA"????? Moving .5" at 100 yards is not acceptable and not a good scope. Movement, no matter how much, is not acceptable.
As far as which scope holds zero, I have had several Leupold Mark4 M1 10x fixed power scopes and none of them ever moved. Back when people first started to shoot shoulder fired 50 cal weapons this was the only scope out there for a good while that would hold zero and not sustain damage from the repeated heavy recoil. Not the best optics in the world, but it wont break or mess up. I would say that the Burris Posi-Loc wont move either.
Not defending anyone's scopes, as any of them can and will fail to maintain zero, but in 40 years of shooting rifles and shotguns with scopes I have only seen 2 that factually failed. I have seen close to 100 that were unjustly blamed for it though....just sayin'
I think what you might be seeing is the upper and lower receivers move in relation to each other when you are dropping the hammer. Very little felt movement between the receivers can really look like a big deal thru a scope, especially if it is turned up in power. Unless you have some kind of "anti movement" device, set screws, {even an Accu-wedge is better than nothing} there will be movement.
What do these scopes look like if you put them on a long action bolt gun and do this dry fire thing?????
