Part one of two ARLINGTON, Va. — Army infantry troops deployed to Afghanistan are struggling to keep weapons clean and in good working order, with soldiers particularly concerned about the maintainability and reliability of the M-4 carbine and the squad automatic weapon, according to an Army report on lessons learned in Afghanistan. But soldiers also are more than pleased with the performance of other weapons, such as the M-240B machine gun, which won a 100 percent vote of confidence overall. And troops often described a love-hate relationship with the same weapon, such as the soldier who called his squad automatic...