9mm Luger, 124gr Maker P-Rex (Pistol Rapid EXpanding) – 20 Rounds

9mm Luger 124gr Maker P-REX – Supersonic Defensive Ammunition

The Just Cause Solutions 9mm Luger 124gr Maker P-REX brings Maker's proven solid copper expanding projectile technology to the most popular defensive handgun cartridge in the world. At 1,100fps from a 4" barrel, the P-REX delivers reliable expansion and controlled penetration — the two performance characteristics that matter most in a defensive load. Whether you're carrying for personal protection, running a duty pistol, or pairing a suppressed host with a quality defensive round, the P-REX is built to perform when it counts.

All of our ammunition is pressure tested using a PCB PIEZOTRONICS Conformal Transducer according to Voluntary Industry Performance Standard as set forth by SAAMI.

Technical Specifications

Barrel Length & Velocity Data

The Maker P-REX Advantage

The P-REX is a monolithic solid copper projectile precision-engineered for reliable expansion in pistol-velocity applications. Unlike traditional jacketed hollow points that rely on a lead core and copper jacket, the P-REX is machined from a single piece of solid copper — eliminating jacket separation and ensuring consistent performance. Key features include:

• Reliable pistol-velocity expansion – Engineered to expand consistently at handgun velocities where some copper designs struggle
• Nearly 100% weight retention – Solid copper construction maintains mass for controlled penetration
• No jacket separation – Monolithic construction eliminates the risk of jacket/core separation common in traditional JHP designs
• CNC-machined precision – Every projectile is machined to exact tolerances for consistent performance and reliable feeding
• Lead-free construction – Cleaner shooting, compliant with lead-free range and hunting regulations where applicable

Application

The 124gr P-REX is designed for shooters who demand premium performance from their 9mm platform. At 1,100fps it meets and exceeds the velocity standard most commonly associated with reliable hollow point expansion, while the solid copper construction ensures that performance is delivered consistently — not just under ideal lab conditions. This load is well-suited for personal defense carry, duty use, and suppressed host pistols where a quality expanding round is required.

Always verify reliable function of any ammunition in your specific firearm before carrying or relying on it for defensive use.

Frequently Asked Questions

Q: Is this appropriate for concealed carry and personal defense?
A: Yes. The P-REX is designed to deliver reliable expansion and controlled penetration — the two primary performance requirements for a defensive handgun load. As with any defensive ammunition, we recommend verifying reliable function in your specific firearm before carrying it.

Q: Will this work in a suppressed 9mm pistol?
A: Yes. At 1,100fps this is a supersonic load, so a sonic crack will be present downrange. The suppressor will reduce muzzle blast and overall sound signature significantly. For a fully suppressed, hearing-safe 9mm experience, a subsonic load would be required.

Q: What makes solid copper better than a traditional jacketed hollow point?
A: Traditional JHP bullets rely on a copper jacket bonded or crimped over a lead core. Under some conditions the jacket and core can separate, reducing penetration and creating unpredictable terminal performance. The P-REX is machined from a single piece of copper — there is no jacket to separate, and weight retention is nearly 100%.

Q: What pistols is this compatible with?
A: The 124gr P-REX is compatible with any 9mm Luger (9x19mm) firearm with a 1:7 to 1:10 barrel twist rate. Most modern 9mm pistols fall within this range. We recommend testing function in your specific firearm before defensive carry or duty use.

Q: How is Just Cause USA's ammunition tested?
A: Every batch we produce is pressure tested using our own PCB PIEZOTRONICS Conformal Transducer according to Voluntary Industry Performance Standard as set forth by SAAMI. This level of in-house testing is uncommon in the industry and reflects our commitment to safety and consistency in every round we release.