Factual error: When in the helicopter the red dot from Miller's sights stays motionless on the EXACT same spot on the man's back - impossible from a helicopter. Doubly so if compared to the scene at the lake, where Miller is sitting totally still and the red dot is moving back and forth over the swimming guy's head.
Factual error: The only railroad in Panama is runing North-South right along the Panama Canal. Not very usable to get "deep into the jungle" - and there are no mountains.
Factual error: When Berenger and Zane are resting, Berenger brings up the "best steelhead fishing" in the state of Montana. Since a steelhead has to migrate to the sea and return to be a steelhead, there is no ocean access to rivers in Montana.
Answer: According to an old post on the Bladeforums website, it was an 8" Al Mar Shadow.