Pure-play defense companies have faced challenging margin conditions in recent years, but are there signs of improvement in recent results?It's been a confusing period for defense companies. While the end-market environment appears conducive to revenue growth, many of the leading defense contractors have notably underperformed the market.That said, three leading defense companies, Lockheed Martin (LMT +0.47%) and the defense businesses of GE Aerospace (GE 0.53%) and RTX (RTX +0.61%), raised their full-year ...