Last reviewed: 2026-04-18 by Jake Terry, FFL07/SOT3, NRA-certified firearms instructor.
When terminal performance and barrier penetration matter, the 10mm Auto 155 grain Hornady XTP brings velocity and expansion in one package. Underwood ammunition pairs the proven Hornady eXtreme Terminal Performance bullet with nickel-plated brass and flash-suppressed propellant, yielding 1500 feet per second and 774 foot-pounds of muzzle energy from a five-inch barrel. 10mm Auto cartridges occupy the middle ground between .40 S&W capacity and .357 Magnum authority — this 155-grain load tilts toward speed over mass, delivering flatter trajectory inside 50 yards and rapid energy transfer on contact. You carry a Glock 20, Springfield XD-M 10mm, or Dan Wesson Razorback because you want margin; this ammunition delivers it.
Built for the Box
Underwood sources Hornady XTP projectiles — a serrated jacket design that controls expansion while the gilding metal-over-lead core drives through heavy clothing and intermediate barriers. Nickel-plated brass casings slide through semi-auto actions without binding, resist tarnish in humid climates, and reload cleanly when you tumble the brass. Boxer primers and non-corrosive propellant mean you store the remaining rounds for years without degradation. Flash-suppressed powder keeps your front sight visible if you fire in dim parking structures or unlit rural driveways. Underwood field-tests each lot in consumer firearms — Glocks, 1911s, revolvers — so feeding and ejection match real-world carry guns, not just SAAMI pressure barrels.
The Numbers
| Spec | Value |
|---|---|
| Caliber | 10mm Auto |
| Bullet weight | 155 grains |
| Bullet type | Hornady XTP jacketed hollow point |
| Muzzle velocity | 1500 fps (5″ test barrel) |
| Muzzle energy | 774 ft-lbs |
| Rounds per box | 20 |
| Case | Nickel-plated brass |
| Primer | Boxer, non-corrosive |
| Reloadable | Yes |
| Intended use | Self-defense, hunting |
| Manufacturer | Underwood Ammunition |
The sectional density of 0.138 reflects the lighter bullet weight — expect rapid expansion and moderate penetration in soft tissue. Ballistic coefficient (G1) of 0.137 matters less at defensive distances; within 25 yards, trajectory drop is negligible. Browse the full Underwood 10mm Ammo catalog to compare this 155-grain load against 180-grain and 200-grain alternatives when barrier penetration outweighs velocity.
Safe Handling & Compliance
Federal law requires purchasers to be at least 21 years old for handgun ammunition. Ammunition cannot be shipped to certain states, counties, and cities — review our ammunition shipping restrictions before ordering. Store ammunition in a cool, dry location away from heat sources and out of reach of unauthorized users.
- Treat every firearm as loaded; keep your finger off the trigger until sights are on target and you have decided to fire; never point the muzzle at anything you are not willing to destroy; be certain of your target and what lies beyond it.
- Verify current state and local ammunition purchase and possession laws in your jurisdiction before ordering.
- This ammunition contains lead; wash hands after handling. California Prop 65 warning applies — see www.P65Warnings.ca.gov for details.
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