My brother has a lead sled and uses it all the time. He loves to brag about dime sized groups with a .17
To me it don't mean a damn thing unless you are holding the rifle.
I can see the utility for working up loads with heavy recoiling rifles. Otherwise all one learns is the potential mechanical accuracy of the rifle. That's pretty meaningless.
When it comes to "real" shooting I can always outscore him. I think the lead sled does more harm than good when marksmanship is considered.
Freedom is not free