Some defense contractors say they're actively pursuing new acquisitions this year, buoyed by greater budget certainty and an early wave of consolidation. Already this year, Orbital Sciences completed its deal to merge with ATK's aerospace and defense businesses, while Engility finalized its purchase of TASC. Earlier this month, Harris announced its plan to buy Exelis to create a 23,000-employee contractor with more than $8 billion in sales. Industry advisers say the trend is likely to continue as companies become more...