About losing your weapons and ammo when exiting bootcamp; I've found a little way around that.
I just passed said River crossing with full size winchesters. I didn't even know they had em until I nicked them off their cold dead bodies. Their guns didn't scare me; their numbers did.
I quickly went up the little hill in the middle and did a lot of hitting and running. Shooting single enemies (without being seen by others) from different angles, and as soon as a second enemy would see me (and aim at me), I would run away and try again somewhere else. Not many were eager enough to chase me up the hill, so I had to do peek-a-boo matches from up top. Those that did chase me were swiftly cut down.
Slave mr. Grumpy even got a few kills with his shotgun. Even if you can't aim like a slave, you can still hit with the benelli. The benelli does the aiming for you! (1:10)