A Philadelphia jury awarded $11 million on Wednesday to a man whose holstered Sig Sauer pistol went off by itself while he was going down the stairs, causing a serious leg injury — the second major verdict this year against the embattled gun manufacturer over its P320 model. After a three-week trial, the jury concluded that New Hampshire-based Sig Sauer was negligent for selling a defective gun and holster. The plaintiff's lawyers said the P320 pistol is prone to going off without the trigger