Sorry but you are incorrect. That land has belonged to the US government since the treaty of Guadalupe Hidalgo. The closest thing to “open range” was that period of time from the 1850’s till the passage of the Taylor Grazing Act in 1934 (before Bundy was born), when the US government did not enforce it’s rights to the land.
Once the grazing act was passed, Congress enforced it’s constitutional authority to determine how that land will be used and what fees were to be collected. Bundy paid those fees until 1993 when he did not like the terms that the land lord (Congress via the BLM) imposed as the legal owners of that land.
You claim the land was appropriated as open range. Show me where Congress appropriated that land as open range. What law or act of congress set aside that land as open range?
I will point out that if there was no appropriation as open range, then they are unappropriated public lands which is exactly what the state constitution says that “they forever disclaim all right and title to”