The FBI Protocol Tests

To pass the FBI protocol, a bullet must be fired through six different barrier types and achieve consistent performance through each: bare ballistic gelatin, heavy winter clothing (4 layers of denim, fleece, cotton), 20-gauge sheet steel (simulating a car door), standard interior wallboard, 3/4" plywood, and laminated automotive windshield glass.

What the FBI Measures

• Penetration (70% weight): Must achieve 12-18 inches in calibrated 10% ballistic gelatin. Under 12" risks failing to reach vital organs. Over 18" risks overpenetration through the target.
• Expansion (20% weight): The bullet must reliably expand (mushroom) to create a larger wound channel. Measured as expanded diameter: a 9mm bullet starts at 0.355".
• Weight retention (10% weight): How much of the bullet's original mass it retains after expansion and barrier penetration. Higher is better, as lost jacket fragments reduce the bullet's effectiveness.

Why FMJ (Ball Ammo) Is Wrong for Defense

Full metal jacket (FMJ) ammunition does not expand. A 9mm FMJ punches a 0.355"-diameter hole through tissue and keeps going, often penetrating 24-30+ inches, which means exiting the target and endangering bystanders. Hollow point ammunition expands to 0.50-0.75", creating a larger wound channel while stopping inside the target within the 12-18" FBI window. Every round of defensive ammunition on this list is a jacketed hollow point (JHP) designed to expand reliably.

1. Function Test in Your Gun

Before trusting any ammunition with your life, fire at least 50-100 rounds of your chosen defensive load through your specific pistol. Defensive hollow points have different feeding profiles than range FMJ. Some pistols are picky about bullet geometry: better to find out at the range than in an emergency. If you can't afford to function-test premium ammo, Hornady XTP ($1.00-1.10/rd) makes this more financially realistic than HST or Gold Dot.

2. Rotate Carry Ammo Every 6-12 Months

Ammunition carried daily is exposed to body heat, humidity, sweat, and repeated chambering/unchambering. Rotate your carry ammo at least annually. When you rotate, shoot the old ammo at the range, which doubles as function testing and practice with your carry load. Modern premium ammo will remain reliable for years in storage, but carried ammo degrades faster. If you want to stay ahead of price spikes during supply chain disruptions, our supply chain preparedness checklist covers when and how much defensive ammo to stock.

3. Avoid Repeated Chambering

Each time you chamber a round, the bullet gets pushed slightly deeper into the case (bullet setback). After 3-5 chambering cycles, the reduced case volume can spike pressure dangerously. Mark your top carry round and track how many times it's been chambered. After 3 cycles, rotate it to the bottom of the magazine and chamber a fresh round.

4. Match Ammo to Your Pistol Size

Full-size / compact pistols (Glock 19, SIG P320, CZ P-10 C): 124gr or 147gr loads, Federal HST, Speer Gold Dot, Hornady Critical Duty. These guns have enough barrel length (3.9-4.5") to generate full velocity from any load.

Subcompact / micro pistols (SIG P365, Glock 43/43X, Hellcat): 115gr or 124gr loads, Hornady Critical Defense 115gr, Federal HST 124gr. Shorter barrels (3.0-3.5") lose 50-100 fps, so lighter bullets that need less velocity to expand are preferred. Avoid +P in subcompacts unless the manufacturer explicitly approves it.