Just had a great life. I was blue and I ran to the green side and made it to an area off to the side of the main battle that hadn't been carved up too bad (most of the rest of the map was either flat or very rough from tons of tunnels and grenades). The best part is, I was to the side of many of the green fortifications. I had spawned right by the tent, so I had the full 80 ammo with 10 in the gun, and I stayed alive until I had used every shot. I kept tunneling around and moving back and forth between foxholes, covering them up as I left them. I had several people come after me, but I just fled down another hole and avoided them until I could catch them off guard from a different side of the hill. I wound up killing 31 people before running out of ammo and rushing someone with my grenades. Sadly, someone who I think just spawned behind me shot me before I got close enough to grenade the two greens I was rushing, who were oblivious to my presence and just hiding in a little bunker shooting at blues across the map.
It only took a body shot, since by then I was down to 8 health from all the near misses (some of which were caused by grenades, had a few people who just started chucking grenades all over the place on me, and they seem to hurt even through walls if you're in close enough proximity). Too bad. Jumping in their bunker and grenading all three of us would have been a good way to end that run.
I think I helped the blue side grab the intel, since I was covering the area where the green intel was and a single blue managed to run through and grab it and run out without getting killed, since all the green bunkers along the way were empty (thanks partly to me shooting their occupants). But I never did see it get captured - not sure if the guy who got it got lost or what, never saw him lose it or finish capturing it after a long time.
Foxholes are definitely the way to get surprise kills. Getting off to the side and making little tunnels and popping up in unexpected places can catch people off guard, and as long as you can do headshots reasonably well you can get a surprising number of kills before being spotted, especially if you keep moving after every kill or two.