The 280 Ackley Improved, widely known as the 280 AI, is a premier high-velocity wildcat cartridge standardized by SAAMI that was originally created by the legendary gunsmith P O Ackley! Developed by taking the standard 280 Remington case and blowing out the shoulder to a sharp 40 degrees while minimizing body taper, it accepts 284-thousandths-inch bullets!By increasing internal powder capacity and allowing the safe firing of standard factory 280 Remington ammunition for fireforming, the 280 Ackley Improved delivers performance that rivals standard 7mm magnums without requiring a magnum bolt face or heavy recoil!
280 Ackley Improved Case Dimensions Overview
| Dimension Property | Specification (Imperial) | Specification (Metric) |
| Parent Case | 280 Remington | 280 Remington |
| Bullet Diameter | 284 thousandths in | 7 mm and 21 hundredths mm |
| Case Length | 2 inches and 525 thousandths | 64 mm and 14 hundredths |
| Case Trim Length | 2 inches and 515 thousandths | 63 mm and 88 hundredths |
| Overall Length (COAL) | 3 inches and 330 thousandths (Max) | 84 mm and 58 hundredths |
| Rim Diameter | 473 thousandths in | 12 mm and 1 hundredth |
| Rim Thickness | 50 thousandths in | 1 mm and 27 hundredths |
| Base Diameter | 470 thousandths in | 11 mm and 94 hundredths |
| Shoulder Diameter | 454 thousandths in | 11 mm and 53 hundredths |
| Neck Diameter | 313 thousandths in | 7 mm and 95 hundredths |
| Shoulder Angle | 40 degrees | 40 degrees |
| Case Capacity | Approx 72 grains water | 4 cubic cm and 67 hundredths |
| Maximum Average Pressure | 65-thousand psi | 448 megapascals |
Understanding the 280 Ackley Improved Case Dimensions
- Parentage: Derived directly from the 280 Remington case family, which shares its lineage with the 30-06 Springfield and retains large rifle primer pockets;
- Sharp Shoulder Geometry:Features Ackley’s signature 40-degree shoulder angle that dramatically reduces body taper, eliminates frequent case stretching, and increases powder volume;
- Headspace Design: Engineered with a specific shoulder datum location that allows standard parent 280 Remington cartridges to headspace safely and fireform accurately inside the improved chamber;
- Action Compatibility: Requires a standard long-action receiver and internal magazine box to handle its maximum overall length of 3 inches and 330 thousandths!
280 Ackley Improved Case Dimensions in Inches and Millimeters
| Measurement Point | Max (Inches) | Min (Inches) | Max (Millimeters) | Min (Millimeters) |
| Case Length | 2 and 525 thousandths | 2 and 475 thousandths | 64 and 14 hundredths | 62 and 86 hundredths |
| Trim-To Length | 2 and 515 thousandths | None | 63 and 88 hundredths | None |
| Rim Diameter | 473 thousandths | 463 thousandths | 12 and 1 hundredth | 11 and 76 hundredths |
| Base Diameter | 470 thousandths | 465 thousandths | 11 and 94 hundredths | 11 and 81 hundredths |
| Shoulder Diameter | 454 thousandths | 449 thousandths | 11 and 53 hundredths | 11 and 40 hundredths |
| Neck Diameter | 313 thousandths | 308 thousandths | 7 and 95 hundredths | 7 and 82 hundredths |
| Bullet Diameter | 284 thousandths | 282 thousandths | 7 and 21 hundredths | 7 and 16 hundredths |
| Overall Length (COAL) | 3 and 330 thousandths | 3 and 150 thousandths | 84 and 58 hundredths | 80 mm |
280 Ackley Improved Case Length
The maximum case length of the 280 Ackley Improved is 2 inches and 525 thousandths (64 mm and 14 hundredths), with a recommended trim-to length of 2 inches and 515 thousandths (63 mm and 88 hundredths)! Because of the sharp 40-degree shoulder design and efficient powder combustion under a maximum operating pressure of 65-thousand psi, brass growth and stretching are significantly reduced compared to standard parent cases! However, handloaders should still measure and trim cases periodically after multiple high-performance firings!
280 Ackley Improved Base and Rim Dimensions
The 280 Ackley Improved retains the reliable standard rim architecture of the 30-06 Springfield family!
- Rim Diameter: 473 thousandths in (12 mm and 1 hundredth)
- Base Diameter: 470 thousandths in (11 mm and 94 hundredths)
- Rim Thickness: 50 thousandths in (1 mm and 27 hundredths)
This standard-size rim ensures that standard long-action bolt faces extract and feed cleanly without needing specialized magnum components or custom bolt face alterations!
280 Ackley Improved Shoulder and Neck Dimensions
- Shoulder Angle:A radical 40 degrees maximizes case capacity and provides an abrupt headspace stop for fireforming parent ammunition safely;
- Shoulder Diameter: Measures 454 thousandths in at the sharp shoulder junction;
- Neck Length & Description: Features a well-proportioned neck measuring 313 thousandths in in diameter, offering excellent concentricity and secure bullet tension for heavy high-BC 7mm projectiles!
280 Ackley Improved Case Capacity
The internal case capacity of the 280 Ackley Improved averages roughly 72 grains of water, providing a substantial boost over the standard parent case and approaching the velocity threshold of belted 7mm magnums!This efficient powder space pairs exceptionally well with medium-slow burning powders like Hodgdon H4831, IMR 7828, and Reloader 22, pushing high-BC bullets to flat-shooting velocities with manageable recoil!
280 Ackley Improved Dimensions vs Similar Cartridges
| Cartridge | Bullet Diameter | Case Length | COAL | Max Pressure |
| 280 Ackley Improved | 284 thousandths | 2 and 525 thousandths | 3 and 330 thousandths | 65-thousand psi |
| 280 Remington | 284 thousandths | 2 and 540 thousandths | 3 and 300 thousandths | 60-thousand psi |
| 270 Winchester | 277 thousandths | 2 and 540 thousandths | 3 and 340 thousandths | 65-thousand psi |
| 7mm Remington Magnum | 284 thousandths | 2 and 500 thousandths | 3 and 290 thousandths | 61-thousand psi |
| 30-06 Springfield | 308 thousandths | 2 and 494 thousandths | 3 and 340 thousandths | 60-thousand psi |
Chamber and Case Dimensions
Chamber dimensions for SAAMI-compliant 280 Ackley Improved rifles are carefully cut to permit the chambering and safe firing of standard 280 Remington factory ammunition for fireforming purposes! The transition radius at the neck and shoulder junction is optimized to form the sharp 40-degree shoulder smoothly when pressure is applied! Handloaders should verify their specific chamber reamer specifications if working with older custom wildcat builds versus modern SAAMI factory rifles!
Common Questions
- Can I fire standard 280 Remington ammunition in a 280 Ackley Improved rifle?Yes! One of the greatest design features created by P O Ackley is that standard parent 280 Remington ammunition can be safely chambered and fired in a 280 AI rifle to fireform the brass into the sharp 40-degree shape!
- What twist rate is ideal for 280 Ackley Improved dimensions?A fast 1 in 8 or 1 in 9 twist rate is strongly recommended to effectively stabilize modern heavy, ultra-long-range 7mm bullets ranging from 150 grains up to 175 grains or higher!
- Does the 280 Ackley Improved require a magnum action?No! Because it utilizes a standard 30-06-sized rim and base architecture, it operates smoothly within standard long-action receivers and internal magazines without needing a heavy magnum bolt face!