Pistol · Proprietary
7mm JDJ
The 7mm JDJ is a SSK Industries wildcat cartridge for the TC Contender, based on the .225 Winchester case necked up to 7mm.
- Caliber
- 0.284″ · 7.214 mm
- Introduced
- 1978
- Case
- Rimless
- Parent
- .225 Winchester
- Primary use
- hunting, handgun_hunting
- Status
- Active
- Introduced
- 1978
- Type
- Pistol
- Origin
- United States
- Inventor
- J.D. Jones
- Manufacturer
- SSK Industries
- Standard
- Proprietary
- Status
- Active
- Availability
- Rare
- Case capacity
- 43.6 gr H₂O
- Twist (typical)
- 1:10
- Primer
- Large Pistol
- Case type
- Rimless
- Max pressure
- 42,000 psi, SAAMI transducer
- Eff. range
- 200 yd
- Max range
- 4000 yd
- Recoil
- 8.5–17.1 ft·lb
Ballistics
Velocity only, no drag model: no published ballistic coefficient is on file for 7mm JDJ, 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
- .225 Winchester
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.
SAAMI · approximate| Measure | mm | in | ✓ |
|---|---|---|---|
| Bullet ⌀ | 7.21 | 0.284 | ~ |
| Neck ⌀ | 7.92 | 0.312 | |
| Shoulder ⌀ | 10.54 | 0.415 | |
| Shoulder angle | 40° | — | ~ |
| Base ⌀ | 10.69 | 0.421 | ~ |
| Rim ⌀ | 12.01 | 0.473 | ~ |
| Belt ⌀ | n/a | ||
| Rim thickness | 1.24 | 0.049 | ~ |
| Neck length | 7.45 | 0.293 | |
| Case length | 48.26 | 1.900 | ~ |
| Overall length | 62.74 | 2.470 | ~ |
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. 7mm JDJ is highlighted below.
Missing a dimension for 7mm JDJ? 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.
Lineage
Connected reference
History
Part of J.D. Jones' original JDJ family designed in the late 1970s, the 7mm JDJ offers similar performance to 7-30 Waters but in a slightly different case design. It is typically ordered as a custom barrel from SSK Industries.
FAQs
- What twist rate does 7mm JDJ use?
- 7mm JDJ typically uses a 1:10 twist rate.
- What bullet diameter is 7mm JDJ?
- 7mm JDJ uses a 0.284″ (7.214 mm) diameter bullet.
- Is 7mm JDJ still in production?
- 7mm JDJ is active; typical availability is rare.
- What is 7mm JDJ used for?
- 7mm JDJ is primarily used for hunting, handgun_hunting.
- What is 7mm JDJ based on?
- 7mm JDJ is derived from the .225 Winchester 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 →
