In competitive shooting, gear rules matter. One of the most-crucial standards in the IDPA world is the dimensional “box” used to verify whether a pistol (with its largest magazine inserted) meets division requirements. This simple physical check can determine whether your pistol is match-legal before you ever hit the first shot.
What is the “IDPA box”?
The IDPA box (also called a “gun test box” or “measuring box”) is a rigid container used in equipment checks. The rule states that, for most handgun divisions, the pistol with the largest magazine inserted must fit wholly inside the box without protruding.
Standard dimensions by division
Here are the key box dimensions by division (as of the current rulebook and appendices):
- SSP / ESP / CDP / CO – The largest standard size: 8 ¾″ × 6″ × 1 ⅝″ (≈ 222 mm × 152.4 mm × 41.3 mm) with the largest magazine inserted.
- CCP (Compact Carry Pistol) – Smaller box: 7 ¾″ × 5 ⅜″ × 1 ⅜″ (≈ 196.8 mm × 136.5 mm × 34.9 mm) with the largest magazine.
- BUG (Back-Up Gun division) – Smallest size: 6 ½″ × 4 ⅝″ × 1 ⅜″ (≈ 165 mm × 117.5 mm × 34.9 mm) with largest magazine inserted.
Why these dimensions matter
- Legal eligibility – If your pistol fails to fit the box for your chosen division, you risk disqualification after first shots are taken. Most Matches will have courtesy checks available (ask before you show up to the match expecting one).
- Modification control – The box dimension rule can limit external size enhancements (mag-wells, extended base pads, oversized safeties) which can give a performance edge but may push you out of compliance. Check the Equipment rules.
- Consistency in equipment checks – Match officials use standardized boxes so that gear across competitors adheres to the same physical constraints.
Tips for preparing your pistol to fit the box
- If you don't have a regulation set of IDPA boxes available, you can buy 3D printed ones like ours! Selfish Plug: IDPA Test Boxes
- Insert the largest legal magazine you intend to use.
- Ensure the slide is fully forward and locked, or in the configuration specified by your division.
- Place the pistol in the box and it is flush without forcing. If forced, the pistol does not fit.
- Pay attention to often-overlooked areas: oversized safeties, beavertails, and mag-well lips often prevent fit.
- Measure early and verify before the day of the match—problems discovered onsite cost time and stress.
Common pitfalls & FAQs
- “I only barely forced it — is that ok?” – No. The rule is clear: the pistol must fit without forcing. If you have to wedge it, rotate it, or remove the magazine, you’re at risk.
- “Is the tolerance +/- allowed?” – The rulebook gives exact numbers; any deviation risks being ruled illegal. Some clubs may accept minor variances, but you should not rely on that.
- “What about optics or threaded barrels?” – For divisions that allow optics (e.g., CO), the same box size is used (8 ¾″ × 6″ × 1 ⅝″) and your optic must not prevent the pistol with magazine from fitting.
The bottom line
Understanding and adhering to the IDPA box dimensions is critical for match prep. If your pistol fits the box for your division with magazine inserted, you’ve cleared one of the most foundational equipment checks. Combine that with proper weight, magazine capacity, and permitted modifications, and you’re ready to compete with confidence.
