I remember in the Aliens director's commentary Cameron said he was the only actor on set with military experience and it kicked in when he saved a few people went a stunt went wrong in the APC and the roof collapsed.
>I spent six years in the United States Marine Corps; I hold thirteen combat awards and decorations, including two purple hearts. I was the first black Marine in the 1st Marine Division in Vietnam to be meritoriously promoted to the rank of sergeant; I served with Kilo Battery, Fourth Battalion, 11th Marines, 1st Marine Division, of that I am very proud.