Another constraint was imposed by the light armament carried by the "Luftwaffe" bombers. At the start of the battle they were still armed with an average of three hand held MG 15 light machine guns, which were supplied by 75 round "saddle drum" magazines. When faced with concentrated attacks by modern fighters such as the Hurricane and Spitfire this proved totally inadequate. Although many of the "Luftwaffe" gunners were well trained and capable of hitting a fast moving fighter the damage done was seldom enough to stop the attack in time to prevent heavy damage being done to the bomber. The high rate of fire of the MG 15 meant that the small magazines emptied quickly; the time taken to reload often gave a fighter the time it needed to make a successful attack. Efforts had been made to increase the number of defensive weapons, but this also meant that because the weapons were hand-held either more crew members were needed in each aircraft, or the existing crew members could be overworked. It was a problem which was never to be fully resolved and the "Luftwaffe" bombers had to rely on the ability of their fighters to protect their formations.