Rifle · Not SAAMI standardized · Not standardizedObsolete
20/577 Alexander Henry
20/577 Alexander Henry is a rimmed bottlenecked rifle cartridge of United Kingdom origin.
- Caliber
- 0.584″ · 14.834 mm
- Introduced
- 1895
- Case
- Rimmed
- Parent
- 20 bore
- Primary use
- Hunting
- Status
- Obsolete
- Obsolete
- Obsolete
- Introduced
- 1895
- Type
- Rifle
- Origin
- United Kingdom
- Inventor
- Alexander Henry
- Manufacturer
- Henry
- Standard
- Not SAAMI standardized · Not standardized
- SAAMI
- Not SAAMI standardized
- Obsolete
- Obsolete
- Status
- Obsolete
- Availability
- Collector
- Case capacity
- 176.7 gr H₂O
- Twist (typical)
- 1:16
- Primer
- Large Rifle Magnum
- Case type
- Rimmed
- Max pressure
- 35,500 psi, CIP transducer
- Eff. range
- 150 yd
- Max range
- 750 yd
- Recoil
- 88.4 ft·lb
Ballistics
Velocity only, no drag model: no published ballistic coefficient is on file for 20/577 Alexander Henry, so this is the shape gravity alone gives the advertised velocity. Drag would steepen it. The tool below solves real loads through their published G1 or G7 model.
Open in Ballistic Compare- Parent case
- 20 bore
Representative trajectory — modeled from a single velocity input (no published BC for this cartridge yet).
Dimensionscase measurements · scale drawing · size vs familiar rounds
Case dimensions — the scale drawing at the top of the page is built from these.
Wikipedia · approximate| Measure | mm | in | ✓ |
|---|---|---|---|
| Bullet ⌀ | 14.83 | 0.584 | · |
| Neck ⌀ | 15.42 | 0.607 | · |
| Shoulder ⌀ | 17.12 | 0.674 | · |
| Shoulder angle | 15° | — | |
| Base ⌀ | 17.93 | 0.706 | · |
| Rim ⌀ | 19.15 | 0.754 | · |
| Belt ⌀ | n/a | ||
| Rim thickness | 1.52 | 0.060 | · |
| Neck length | 11.62 | 0.457 | |
| Case length | 69.85 | 2.750 | · |
| Overall length | 83.06 | 3.270 | · |
Size vs familiar rounds
Drawn at true 1:1 — every case is accurate relative to the others. Absolute size depends on your screen's pixel density, so measuring one against a real ruler may be off. 20/577 Alexander Henry is highlighted below.
Missing a dimension for 20/577 Alexander Henry? Some case measurements aren't in a published SAAMI/CIP drawing yet. Have a factory or reamer print? Send it → — verified hard-to-find data earns a free Lindcott sticker.
Reloading costestimate cost per round vs factory
Estimate your cost per round and how it compares to factory. Inputs are yours — nothing is stored.
Cost estimate only — not load data. Charge weight is your input; follow published manuals for safe charges.
Connected reference
History
Introduced around 1895 by Alexander Henry, derived from the 20 bore.
FAQs
- What twist rate does 20/577 Alexander Henry use?
- 20/577 Alexander Henry typically uses a 1:16 twist rate.
- What bullet diameter is 20/577 Alexander Henry?
- 20/577 Alexander Henry uses a 0.584″ (14.834 mm) diameter bullet.
- Is 20/577 Alexander Henry still in production?
- 20/577 Alexander Henry is obsolete; typical availability is collector.
- What is 20/577 Alexander Henry used for?
- 20/577 Alexander Henry is primarily used for hunting.
- What is 20/577 Alexander Henry based on?
- 20/577 Alexander Henry is derived from the 20 bore case.
Sources & provenance
Data & sources. Specs compiled from the Lindcott Armory reference; the trajectory is modeled (point-mass), not measured. See methodology. Spotted an error? Report it →
