Conversion Guide
A table showing the various gauge sizes with weights. The bores marked * are found in punt guns and rare weapons only. The .410 bore and 23mm caliber are exceptions; they are actual bore sizes, not gauges. If the .410 and 23mm were measured traditionally, they would be 67.62 gauge and 6.278 gauge, respectively.
| Gauge (Bore) |
Diameter | Weight of unalloyed (pure) lead ball | |||
|---|---|---|---|---|---|
| (mm) | (in) | grams | ounces | grains | |
| AA* | 101.60 | 4.000 | 6225.52 | 219.6 | 96,080 |
| A½* | 76.20 | 3.000 | 2626.39 | 92.64 | 40,530 |
| 0.25* | 67.34 | 2.651 | 1814.36 | 64.000 | 28,000 |
| 0.5* | 53.45 | 2.103 | 907.18 | 32.000 | 14,000 |
| A* | 50.80 | 2.000 | 778.19 | 27.45 | 12,010 |
| 0.75* | 46.70 | 1.838 | 604.80 | 21.336 | 9328 |
| 1* | 42.42 | 1.669 | 453.59 | 16.000 | 7000 |
| B½* | 38.10 | 1.500 | 328.3 | 11.58 | 5066 |
| 1.5* | 37.05 | 1.459 | 302.39 | 10.667 | 4667 |
| 2* | 33.67 | 1.326 | 226.80 | 8.000 | 3500 |
| 3* | 29.41 | 1.158 | 151.20 | 5.333 | 2333 |
| 4* | 26.72 | 1.052 | 113.40 | 4.000 | 1750 |
| B* | 25.40 | 1.000 | 97.27 | 3.43 | 1501 |
| 5* | 24.80 | .976 | 90.72 | 3.200 | 1400 |
| 6* | 23.35 | .919 | 75.60 | 2.667 | 1166 |
| 6.278 | 23.00 | .906 | 72.26 | 2.549 | 1114 |
| 7* | 22.18 | .873 | 64.80 | 2.286 | 1000 |
| 8 | 21.21 | .835 | 56.70 | 2.000 | 875 |
| 9* | 20.39 | .803 | 50.40 | 1.778 | 778 |
| 10 | 19.69 | .775 | 45.36 | 1.600 | 700 |
| 11/C½* | 19.05 | .750 | 41.24 | 1.454 | 636 |
| 12 | 18.53 | .729 | 37.80 | 1.333 | 583 |
| 13* | 18.04 | .710 | 34.89 | 1.231 | 538 |
| 14* | 17.60 | .693 | 32.40 | 1.143 | 500 |
| 15* | 17.21 | .677 | 30.24 | 1.067 | 467 |
| 16 | 16.83 | .663 | 28.35 | 1.000 | 438 |
| 17* | 16.50 | .650 | 26.68 | 0.941 | 412 |
| 18* | 16.19 | .637 | 25.20 | 0.889 | 389 |
| 20 | 15.63 | .615 | 22.68 | 0.800 | 350 |
| 22* | 15.13 | .596 | 20.62 | 0.728 | 319 |
| 24* | 14.70 | .579 | 18.90 | 0.667 | 292 |
| 26* | 14.31 | .564 | 17.44 | 0.615 | 269 |
| 28 | 13.97 | .550 | 16.20 | 0.571 | 250 |
| 32* | 13.36 | .526 | 14.17 | 0.500 | 219 |
| 36 | 12.85 | .506 | 12.59 | 0.444 | 194 |
| C* | 12.70 | .500 | 12.16 | 0.429 | 188 |
| 40 | 12.40 | .488 | 11.34 | 0.400 | 175 |
| 67.62 | 10.41 | .410 | 6.71 | 0.237 | 104 |
Note: Use of this table for estimating bullet masses for historical large-bore rifles is limited, as this table assumes the use of round ball, rather than conical bullets; for example, a typical 4 bore rifle from circa 1880 used a 2,000-grain (4.57 oz) bullet, or sometimes slightly heavier, rather than using a 4 ounce round lead ball. (Round balls give progressively much worse external ballistic performance than conical bullets at ranges greater than about 75 yards.) In contrast, a 4-bore express rifle often used a 1,500-grain (3.43 oz) bullet wrapped in paper to keep lead buildup to a minimum in the barrel. In either case, assuming a 4-ounce mass for a 4-bore rifle bullet from this table would be inaccurate, although indicative.
Read more about this topic: Gauge (bore Diameter)
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