The ammunition caliber in Crimson Skies are often stated just as 30, which is short for 0.30 inches. This is easily converted to the more convenient metric system by multiplying with 25,4.
| CS style | Inches | Metric |
| 30 | 0.30 | 7.62 mm |
| 40 | 0.40 | 10.16 mm |
| 50 | 0.50 | 12.70 mm |
| 60 | 0.60 | 15.24 mm |
| 70 | 0.70 | 17.78 mm |