As the British you will have to clear out a building. When you clear it out, go up to the upstairs area and move to your right. You will find a little room. When you get to the entrance, look to the left to find three KAR98Ks and three MP40s. You can pick those up whenever desired, and they respawn. Collect them if you are low on ammunition, then return there again when you need to restock.