"Shinchoko-ki" by Gyuichi OTA does not mention 3,000 teppo but it does mention that '千挺計' (about 1,000 teppo) were used in the main battle and '五百挺' (500 teppo) were used by the detachment force in the Battle on Mt. Tobigasu (making a total of about 1,500).
大田牛一の『信長公記』では、決戦に使用された鉄砲数に関しては「千挺計」（約1000丁）、鳶ヶ巣山攻撃の別働隊が「五百挺」と書いてあり（計約1500丁）、3000丁とは書かれてない。