Question: what is the difference between a 40 and 45 caliber?
Answer: 40 has a bullet diameter of 10.2mm (. 400 in), a neck diameter of 10.7mm, a shoulder diameter of 10.7 mm, a base diameter of 10.8mm, a rim diameter of 10.8mm and a rim thickness of 1.4mm. The . 45 has a bullet diameter of 11.5 mm (.