I'm sure most of you have already discovered how to do this, since it's really rather easy when you think about it, but here goes.
On Omaha Beach, simply avoid picking up the Sniper Rifle on your way from the base of the bunker to the trench. Thus, when you get into the bunker, the Rifle slot in your inventory will be empty, and you be free to pick up the german one.
It's a bit of a waste of time, considering the circumstances, but it's a nice change
