Mont. Code § 82-2-114
If, at any time, the locator of a mining claim or the locator's successors or assigns determine that the original declaratory statement was defective or erroneous, determine that the requirements of law were not complied with, or want to change the boundaries or take in any part of an overlapping claim that has been abandoned or if the original declaratory statement was filed prior to the passage of this law and the locator or the locator's successor's or assigns want the benefit of this part, the locator or the successors or assigns may file an additional or amended declaratory statement subject to the provisions of this part. However, the relocation or filing of the amended or additional declaratory statement may not interfere with the existing rights of others at the time of the relocation or filing of the amended or additional declaratory statement, and the relocation or amended or additional declaratory statement or other record may not preclude the claimant or claimants from proving any title that the claimant may have held under the previous location and notice.
§ 82-2-114, MCA