Rifle · Wildcat
6mm-284
Legendary benchrest and long-range competition wildcat.
- Caliber
- 0.243″ · 6.172 mm
- Introduced
- 1960
- Case
- Rebated
- Parent
- .284 Winchester
- Primary use
- Competition, Target
- Status
- Limited
- Introduced
- 1960
- Type
- Rifle
- Origin
- United States
- Inventor
- Benchrest shooters
- Manufacturer
- Various wildcatters
- Standard
- Wildcat
- Status
- Limited
- Availability
- Scarce
- Case capacity
- 71 gr H₂O
- Twist (typical)
- 1:8 to 1:10
- Primer
- Large Rifle
- Case type
- Rebated
- Max pressure
- 62,000 psi
- Eff. range
- 1000 yd
- Max range
- 4200 yd
- Recoil
- 5–8 ft·lb
Ballistics
Published velocity/energy data isn't available for 6mm-284. Parent case: .284 Winchester.
Performance
Dimensionscase measurements · scale drawing · size vs familiar rounds
Case dimensions — the scale drawing at the top of the page is built from these.
SAAMI · verified| Measure | mm | in | ✓ |
|---|---|---|---|
| Bullet ⌀ | 6.17 | 0.243 | ✓ |
| Neck ⌀ | 7.01 | 0.276 | ✓ |
| Shoulder ⌀ | 12.06 | 0.475 | ✓ |
| Shoulder angle | 35° | — | ✓ |
| Base ⌀ | 12.70 | 0.500 | ✓ |
| Rim ⌀ | 12.01 | 0.473 | ✓ |
| Belt ⌀ | n/a | ||
| Rim thickness | 1.37 | 0.054 | ✓ |
| Neck length | 7.24 | 0.285 | ≈ |
| Case length | 55.12 | 2.170 | ✓ |
| Overall length | 71.12 | 2.800 | ✓ |
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. 6mm-284 is highlighted below.
Factory loads
Being verified
Advertised FPS, energy, and BC are withheld until loads clear verification.
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
Developed in 1960s by benchrest shooters seeking extreme accuracy. Necking .284 Winchester to 6mm created high-velocity, high-capacity case in short action. Dominated long-range competition for 30+ years. Never commercialized but remained popular wildcat. Inspired development of 6.5-284 Norma. The 6mm Creedmoor is essentially a commercial version of this concept. Still used by some long-range competitors.
FAQs
- What twist rate does 6mm-284 use?
- 6mm-284 typically uses a 1:8 to 1:10 twist rate.
- What bullet diameter is 6mm-284?
- 6mm-284 uses a 0.243″ (6.172 mm) diameter bullet.
- Is 6mm-284 still in production?
- 6mm-284 is limited; typical availability is scarce.
- What is 6mm-284 used for?
- 6mm-284 is primarily used for competition, target.
- What is 6mm-284 based on?
- 6mm-284 is derived from the .284 Winchester case.
Sources & provenance
Data & sources. Specs compiled from the Lindcott Armory reference; availability counted from 20 live factory loads; the trajectory is modeled (point-mass), not measured. See methodology. Spotted an error? Report it →