Mont. Code Ann. § 82-2-109

When a locator or claimant amends or relocates the locator's or claimant's own claim, the amendment or relocation may not be construed as a waiver of any right or title acquired by the locator or claimant by virtue of the previous location or record of that location, except as to portions of the previous location that may be omitted from the boundaries of the claim as amended or relocated. As to the portion of ground included both in the original location and the location as amended or relocated, the locator or claimant may rely either upon the original location or the location as amended or relocated or upon both. However, this section may not be construed as permitting the locator or claimant to hold a tract that does not include a valid discovery.