Vascular access system embodiments can be configured to remove gas and a piercing member from a catheter assembly. In some embodiments, vascular access systems can remove gas and at least a portion of a piercing member concurrently or simultaneously. In some embodiments, vascular access systems can remove gas before removing at least a portion of a piercing member. In several embodiments, a vascular access system can include a first barrel configured to remove gas and a second barrel configured to retract a piercing member.