Ammo & Ballistics
Explained
What every bullet type actually does, how terminal performance works, how to match caliber to use case, and what overpenetration really means for home defense. No jargon — just what you need to make an informed decision.
The FBI developed a standardized terminal performance test protocol used industry-wide to evaluate defensive ammunition. Rounds are tested through 6 barrier types: bare gelatin, heavy clothing, steel, wallboard, plywood, and auto glass — then into 10% ballistic gelatin blocks that simulate soft tissue.
The FBI standard calls for 12–18 inches of penetration in bare gelatin with reliable expansion to at least 1.5x original diameter. Rounds that meet this standard are consistently the top performers in real-world use.
Why 12–18 inches? Less than 12" risks insufficient penetration to reach vital structures through an arm, heavy clothing, or oblique angle. More than 18" raises overpenetration concerns in a home defense context.
Overpenetration — a defensive bullet passing through the target and continuing — is a genuine consideration for home defense, but it's often overstated as a reason to choose "weaker" loads. A bullet that doesn't penetrate enough to reach vital structures is far less effective at stopping a threat.
A well-designed JHP in a service caliber (9mm, .40, .45) will typically stop expanding and lose energy after 14–16 inches of gelatin. That said, any bullet can overpenetrate in specific scenarios.
FMJ penetrates more than JHP. If you're worried about overpenetration, use a quality JHP — not FMJ. FMJ doesn't expand, travels faster through soft tissue, and exits with far more retained energy than an expanded JHP.
| Caliber | Primary Use | Defensive Load Recommendation | Notes |
|---|---|---|---|
| .22 LR | Training, small game, plinking | CCI Mini-Mag HP for small game. Not a primary defensive caliber. | Low recoil makes it ideal for new shooter training. Rimfire ignition is less reliable than centerfire — not recommended as primary defensive caliber. |
| .380 ACP | Deep concealment, backup | Hornady Critical Defense 90gr FTX, Speer Gold Dot 90gr | Marginal at the lower end of defensive performance. Use only with proven expanding loads. Short barrels reduce velocity — choose loads designed for short barrels. |
| 9mm Luger | EDC, duty, home defense, training | Federal HST 124gr +P, Speer Gold Dot 124gr, Hornady Critical Duty 135gr | The current consensus best all-around defensive caliber. Outstanding terminal performance, manageable recoil, high capacity. Modern JHPs perform on par with larger calibers in FBI testing. |
| .40 S&W | Duty, EDC (legacy) | Federal HST 180gr, Speer Gold Dot 180gr | More recoil than 9mm with limited capacity advantage. Still a proven performer. Declining in new platform development but existing firearms are fully capable. |
| .45 ACP | EDC, home defense, competition | Federal HST 230gr, Hornady Critical Defense 185gr FTX | Large diameter, subsonic — naturally suppressor-compatible. Excellent terminal performance at the cost of magazine capacity. Proven generational track record. |
| 10mm Auto | EDC, backcountry, hunting | Hornady Critical Duty 175gr, Federal HST 200gr | Highest energy of common handgun calibers. Effective on large animals for backcountry carry. Manageable in full-size platforms. Overkill for indoor home defense. |
| .38 Special | Revolver EDC, backup | Hornady Critical Defense +P 110gr FTX, Federal HST 130gr | Standard pressure .38 from a short barrel is marginal. Use +P loads from a quality revolver. Better suited to medium-frame revolvers than J-frames. |
| .357 Magnum | EDC revolver, hunting, bear defense | Federal HST 130gr (out of .38Spl cylinder), or carry .357 125gr JHP | Significant terminal performance advantage over .38 Special. Proven manstopper. Loud unsuppressed — significant blast in indoor environments. |
| 5.56 NATO | Home defense rifle, patrol, hunting | Federal 55gr JSP (for hunting), Hornady TAP 75gr (defense) | At home defense velocities through 16"+ barrels, 5.56 fragments reliably and penetrates walls less than many expect. Use soft points or TAP-style loads — M193 or M855 can overpenetrate depending on construction. |
| .300 BLK Subsonic | Suppressed home defense, hunting | Hornady Sub-X 190gr, SIG Sauer 220gr OTM | Specifically designed for suppressed use. Subsonic means no supersonic crack. Terminal performance at subsonic velocity is lower than supersonic rifle calibers — choose expanding loads specifically designed for subsonic use. |
| .308 Winchester | Hunting, precision, designated marksman | Hornady GMX 165gr (hunting), Federal Gold Medal 175gr SMK (precision) | Overpenetration concern in home defense context. Appropriate for rural property defense, hunting, and precision use. Not ideal for urban home defense. |
| 12 Gauge | Home defense, hunting | Federal FliteControl 00 Buck (defense), Federal Power-Shok slug (long range) | 00 buckshot delivers 9 .33-caliber pellets per shot — devastating terminal effect. FliteControl wad keeps patterns tighter at range. #4 buck penetrates walls less than 00 — a consideration in occupied structures. |
Grain (gr) is the unit of bullet weight. Heavier bullets are slower for the same powder charge, lighter bullets are faster. In handgun calibers, heavier typically means more reliable expansion in a JHP and better penetration. Lighter typically means higher velocity and flatter trajectory.
Standard weights by caliber: 9mm is typically 115gr, 124gr, or 147gr. .45 ACP is typically 185gr or 230gr. 5.56 is typically 55gr or 62gr. There's no universal "best" weight — it depends on intended use.
+P ammo is loaded to a higher-than-standard pressure (SAAMI standard + 10%). +P+ is higher still — not a SAAMI standard, manufacturer-specific. Higher pressure means higher velocity and typically better terminal performance from short barrels.
Not all firearms are rated for +P. Compact and subcompact pistols — especially older designs — may not be. Check your owner's manual. Continuous use of +P accelerates wear on springs, barrels, and frames. Carry +P, train with standard pressure.
Never use +P ammo in a firearm not rated for it. Pressure exceeds the SAAMI spec the firearm was designed around. Check the owner's manual — if it doesn't list +P compatibility, assume it isn't.
Muzzle velocity (fps) measures how fast the bullet leaves the barrel. Muzzle energy (ft-lbs) measures how much kinetic energy it carries — calculated from velocity and bullet weight. Energy is a better indicator of terminal potential than velocity alone.
Example: A 115gr 9mm at 1,200 fps carries about 368 ft-lbs. A 147gr 9mm at 1,000 fps carries about 326 ft-lbs. The lighter, faster load carries more energy — but the heavier load may penetrate deeper and expand more reliably at subsonic speeds.
BC measures how efficiently a bullet retains velocity as it travels through air. Higher BC = less drag = less velocity loss over distance. Matters significantly for rifle shooting beyond 200 yards. For defensive handgun use at typical engagement distances (under 25 yards), BC is irrelevant.
For precision rifle use, a higher BC bullet (typically a heavier, boattail design like Sierra MatchKing or Hornady ELD-M) will drift less in wind and drop less between 300–1000 yards than a lower BC projectile at the same caliber.
This guide is for general reference and educational purposes only. Terminal performance, penetration, and expansion data can vary significantly between firearms, barrel lengths, and testing conditions. Published ballistic data comes from manufacturer testing and may not match real-world results in every situation. HexCore Mounts LLC makes no warranty regarding accuracy or completeness of this information. Ammunition selection for defensive use should be based on thorough personal research including verified testing data. HexCore Mounts LLC is not responsible for any errors, omissions, or actions taken in reliance on information contained herein.
