Cartridge mass
The mass of one loaded round from its bullet and its case, fitted to cartridges whose mass a source states.
The model
The loaded-weight check does not guess what a magazine of rounds weighs: it works it out from the cartridge, with a model fitted to cartridge masses that sources state.
where
- the case envelope, the cylinder the case occupies, in cm³
- the case's base diameter and length, in cm
- the mass of one loaded round and of its bullet, in g
- case and powder per cm³ of envelope, fitted to published cartridge masses; its bounds allow for rimfire and the largest rounds
Cartridge brass (C26000) is 8.53 g per cm³ and smokeless powder 0.8 to 1.0 g per cm³ in bulk; the fitted 2.5 g per cm³ sits between them because the case wall and head fill only part of the envelope.
Fitted to published cartridges
Each row is a cartridge whose loaded mass a source states. The prediction uses only the bullet and the catalogue's own case dimensions; every one lands within 10%.
| Load | Published | Predicted | Off by | Source |
|---|---|---|---|---|
| .45 ACPM1911 ball | 21.19 g | 21.45 g | +1.2% | man.fas.org |
| 5.56×45mm NATOM855 | 12.31 g | 12.08 g | −1.9% | en.wikipedia.org |
| 7.62×39mm57-N-231 | 16.30 g | 17.69 g | +8.5% | en.wikipedia.org |
| 7.62×51mm NATOM80 ball | 25.40 g | 23.66 g | −6.9% | en.wikipedia.org |
Answer: 21.45 g is within 10% of the published 21.19 g, so the model holds for this round.
Checks that use this method
Findings this method raised
Every task the check resting on this method put on the review queue, open and closed, with where each one stands.
Reading the findings…