A lock mandrel installation method, comprising: attaching a lock mandrel to a running tool (160, 300), the lock mandrel having a housing defining a bore with a downhole groove therein, and a key disposed on the housing, the key biased from a retracted condition to an extended condition and having a shoulder facing a downhole end of the housing; holding an inner mandrel in a downhole position in the lock mandrel with the running tool (160, 300), the inner mandrel disposed in the housing and biased to move from the downhole position to an uphole position in the housing, the inner mandrel having a finger and a flange, the finger engaging the downhole groove to hold the inner mandrel in the downhole position; running in the lock mandrel with the running tool (160, 300), the running tool detachably connecting to the housing; engaging the biased key disposed on the lock mandrel against a landing nipple profile while running in the lock mandrel; releasing the hold on the inner mandrel during the engagement of the biased key against the landing nipple profile by: (i) pushing downhole on the running tool (160, 300), (ii) breaking at least one shear pin of the running tool (160, 300) with downhole movement when the shoulder of the key engages in the landing nipple profile, (iii) moving a portion of the running tool (160, 300) relative to the housing when the shoulder of the key in the extended condition engages in the landing nipple profile while running downhole, the moving portion of the running tool (160, 300) having a collet releasing temporary hold on the finger of the inner mandrel in the downhole groove, and (iv) permitting the inner mandrel to move to the uphole position; biasing the released inner mandrel to the uphole position in the lock mandrel; locking the biased key in the landing nipple profile using the flange of the inner mandrel in the uphole position, the flange moving with the inner mandrel and holding the key in the extended condition when in the uphole position; and detaching the running tool (160, 300) from the lock mandrel by pulling uphole on the running tool (160, 300). attaching a lock mandrel to a running tool (160, 300), the lock mandrel having a housing defining a bore with a downhole groove therein, and a key disposed on the housing, the key biased from a retracted condition to an extended condition and having a shoulder facing a downhole end of the housing; holding an inner mandrel in a downhole position in the lock mandrel with the running tool (160, 300), the inner mandrel disposed in the housing and biased to move from the downhole position to an uphole position in the housing, the inner mandrel having a finger and a flange, the finger engaging the downhole groove to hold the inner mandrel in the downhole position; running in the lock mandrel with the running tool (160, 300), the running tool detachably connecting to the housing; engaging the biased key disposed on the lock mandrel against a landing nipple profile while running in the lock mandrel; releasing the hold on the inner mandrel during the engagement of the biased key against the landing nipple profile by: (i) pushing downhole on the running tool (160, 300), (ii) breaking at least one shear pin of the running tool (160, 300) with downhole movement when the shoulder of the key engages in the landing nipple profile, (iii) moving a portion of the running tool (160, 300) relative to the housing when the shoulder of the key in the extended condition engages in the landing nipple profile while running downhole, the moving portion of the running tool (160, 300) having a collet releasing temporary hold on the finger of the inner mandrel in the downhole groove, and (iv) permitting the inner mandrel to move to the uphole position; biasing the released inner mandrel to the uphole position in the lock mandrel; locking the biased key in the landing nipple profile using the flange of the inner mandrel in the uphole position, the flange moving with the inner mandrel and holding the key in the extended condition when in the uphole position; and detaching the running tool (160, 300) from the lock mandrel by pulling uphole on the running tool (160, 300).