Hornady Lock-N-Load Modified Case - 6mm ARC Rifle Brass (A6MMA)

The Hornady Lock-N-Load Modified Case in 6mm ARC is a precision reloading accessory engineered for shooters who demand consistency in handload development. This modified case works with Hornady's Lock-N-Load Precision gauges—specifically the O.A.L. (Overall Length) Gauge—to give you repeatable, accurate cartridge measurements to within .001". If you're developing loads for a new rifle or fine-tuning ammunition for long-range shooting, a properly measured O.A.L. is foundational to safe, accurate results.

The 6mm ARC case itself is specially prepared to serve as a reference standard. A fine-threaded connection at the case head screws securely into your gauge, holding the case perfectly square every time you take a measurement. The neck is opened and slightly oversized—.002" larger than standard—so that a finished bullet slides in smoothly and concentrically without binding or cocking to the side. That concentricity matters: it ensures your gauge reading reflects the actual dimension your reloaded round will have in the chamber, not a skewed measurement caused by a bullet sitting crooked in the case mouth.

Load development for the 6mm ARC benefits from this precision approach, especially for hunters and precision rifle competitors pushing velocity or exploring new powders and primers. By using this modified case with the same bullet weight and profile you plan to load, you capture true O.A.L. data before committing powder and primers to practice rounds. The case meets SAAMI specifications and threads onto both Lock-N-Load O.A.L. gauge models, making it a versatile tool in any reloader's bench setup.

Key Features

• Fine-threaded case head for secure, square attachment to Lock-N-Load Precision gauges
• .002" oversized neck for concentric bullet seating without binding
• Delivers O.A.L. measurements accurate to .001"
• Use with the same bullet profile and weight as your finished loads for true chamber dimensions
• SAAMI-specification brass
• Compatible with both Lock-N-Load O.A.L. gauge models

Specifications

Frequently Asked Questions

What is a modified case, and why do I need one for an O.A.L. gauge?

A modified case is a precision reference tool, not a cartridge for firing. Its oversized, rounded neck allows a bullet to sit concentrically (straight and centered) without tilting, and its threaded base locks it square in the gauge. This ensures your O.A.L. measurement matches the actual dimension your reloaded cartridge will have in your rifle's chamber—critical for safe, consistent loads.

Do I need to use a 6mm ARC modified case if I'm loading 6mm ARC ammunition?

Yes. The modified case is caliber-specific. It must match the cartridge you're loading to give you accurate chamber dimensions for that particular rifle and round.

Will this modified case work with my Lock-N-Load O.A.L. gauge?

Yes. The 6mm ARC modified case is compatible with both Lock-N-Load Precision O.A.L. gauge models via its threaded case-head connection.

What bullet should I use in this modified case?

Use a bullet of the same weight and profile (ogive shape) as the bullets you intend to load. This ensures your O.A.L. measurement is accurate for your actual finished ammunition. The gauge and case are not included in this product; you'll need your own O.A.L. gauge and bullets.