Rifle · Obsolete / Non-standard
.303 Magnum
Holland & Holland's early magnum experiment in .30 caliber — a rimmed cartridge on the large H&H case that predated the .300 H&H Magnum by decades.
- Caliber
- 0.312″ · 7.925 mm
- Introduced
- 1896
- Case
- Rimmed
- Parent
- .276 Enfield
- Primary use
- Hunting, Target
- Status
- Obsolete
- Introduced
- 1896
- Type
- Rifle
- Origin
- United Kingdom
- Inventor
- Holland & Holland
- Manufacturer
- Kynoch (historical)
- Standard
- Obsolete / Non-standard
- Status
- Obsolete
- Availability
- Collector Only
- Case capacity
- 70 gr H₂O
- Twist (typical)
- 1:10
- Primer
- Large Rifle
- Case type
- Rimmed
- Max pressure
- 48,000 psi
- Eff. range
- 1000 yd
- Max range
- 1500 yd
- Recoil
- 18–25 ft·lb
Ballistics
Published velocity/energy data isn't available for .303 Magnum — an obsolete/collector cartridge. Parent case: .303 British.
Performance
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 ⌀ | 7.92 | 0.312 | · |
| Neck ⌀ | 8.76 | 0.345 | · |
| Shoulder ⌀ | 11.73 | 0.462 | ~ |
| Shoulder angle | — | — | |
| Base ⌀ | 13.46 | 0.530 | ~ |
| Rim ⌀ | 14.15 | 0.557 | · |
| Belt ⌀ | n/a | ||
| Rim thickness | — | — | |
| Neck length | — | — | |
| Case length | 59.69 | 2.350 | · |
| Overall length | 85.09 | 3.350 | · |
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. .303 Magnum is highlighted below.
Missing a dimension for .303 Magnum? 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.
Factory loads
Being verified
Advertised FPS, energy, and BC are withheld until loads clear verification.
Suitable powders
1 reloading powder listed for .303 Magnum, fastest to slowest. Cross-reference in the finder →
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.
Lineage
Connected reference
History
Holland & Holland introduced the .303 Magnum in 1896 as a high-velocity .30-caliber hunting cartridge on their large rimmed case. The cartridge delivered dramatically higher velocity than the standard .303 British, making it suitable for long-range plains game hunting in Africa and India. It enjoyed a modest following among serious sporting hunters of the Edwardian era. The development of the .375 H&H Magnum (1912) and then the .300 H&H Magnum (1925) — both on the belted case that became H&H's signature — gradually eclipsed the .303 Magnum. No current production exists; it appears occasionally in original Kynoch ammunition lots at auction and is collected for its historical role in the H&H magnum lineage.
FAQs
- What twist rate does .303 Magnum use?
- .303 Magnum typically uses a 1:10 twist rate.
- What bullet diameter is .303 Magnum?
- .303 Magnum uses a 0.312″ (7.925 mm) diameter bullet.
- Is .303 Magnum still in production?
- .303 Magnum is obsolete; typical availability is collector only.
- What is .303 Magnum used for?
- .303 Magnum is primarily used for hunting, target.
- What is .303 Magnum based on?
- .303 Magnum is derived from the .303 British case.
- What are the best powders for .303 Magnum?
- Reloading powders commonly listed for .303 Magnum include Reloader 19.
Sources & provenance
- Secondary .303 Magnum - Wikipedia · parent_cartridge
Data & sources. Specs compiled from the Lindcott Armory reference; availability counted from 7 live factory loads; the trajectory is modeled (point-mass), not measured. See methodology. Spotted an error? Report it →