During the landing rollout, the right main landing gear collapsed and the airplane veered to the right, which resulted in substantial damage to the horizontal stabilizer. Postaccident examination revealed that the landing gear electric motor would deactivate prematurely due to a faulty pressure switch that prevented full extension of the landing gear. No other landing gear anomalies were observed, including during manual operation of the landing gear hand pump. A landing gear maintenance discrepancy was recorded as “landing gear slow to operate, sometimes need to use handpump” during the last annual inspection. Maintenance personnel troubleshot the landing gear discrepancy and identified a pressure switch to be out of tolerance at 1,100 psi and shimmed the switch to 1,500 psi. During the approach to landing, the pilot recalled that the green landing gear down light was on and he did not hear the landing gear warning horn; however, both the landing gear down light and warning horn tested normally during the examination.