Last reviewed: 2026-04-18 by Jake Terry, FFL07/SOT3, NRA-certified firearms instructor.
Underwood 10mm 220 grain flat nose ammunition is a hard cast load engineered for deep penetration in dense game. The 220 grain flat nose bullet launches at 1200 feet per second from a 5-inch test barrel, generating 704 foot-pounds of muzzle energy. That velocity and sectional density combination drives the projectile through heavy bone and muscle while maintaining nose-forward orientation — critical when you face wild hogs, black bears, or other large predators in the woods. The flat nose design creates a larger permanent wound channel than round nose bullets while the hard cast construction resists deformation on impact, ensuring the bullet tracks straight through the target.
Built for the Box
Each round is loaded in nickel plated brass cases with Boxer primers, making them corrosion-resistant and reloadable. The nickel plating process Underwood uses — Ducta-Bright 7a — eliminates the embrittlement issues that plagued earlier nickel-coated ammunition, so you can reload these cases as many times as raw brass. The hard cast bullets wear a polymer-based “Black Cherry” coating that prevents lead-to-bore contact and resists gas cutting at the base, eliminating lead fouling even at this load’s pressure level. Flash-suppressed powder protects your night vision if you fire in low light. All ammunition is new production, non-corrosive, and assembled in the United States.
Specs at a Glance
| Spec | Value |
|---|---|
| Caliber | 10mm Auto |
| Bullet weight | 220 grains |
| Bullet type | Flat Nose (hard cast, “Black Cherry” coated) |
| Muzzle velocity | 1200 fps (5-inch barrel) |
| Muzzle energy | 704 ft-lbs |
| Rounds/box | 20 |
| Case | Nickel Plated Brass |
| Primer | Boxer |
| Corrosive | No |
| Reloadable | Yes |
| Intended use | Self Defense / Woods Defense |
This load sits at the heavy end of the 10mm Auto spectrum, prioritizing penetration over expansion. If you hunt in bear country or work in wild hog habitat, you want a bullet that punches deep and tracks straight — this is that bullet. For more hard cast and hunting loads, browse our full Underwood 10mm Ammo lineup.
Safe Handling & Compliance
Federal law requires purchasers to be at least 18 years old for rifle and shotgun ammunition, and at least 21 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.
- Observe the four rules of firearm safety: treat every gun as loaded, never point at anything you do not intend to shoot, keep your finger off the trigger until ready to fire, and be certain of your target and what lies beyond it.
- Verify current federal, state, and local laws before purchasing or possessing ammunition — regulations vary by jurisdiction.
- This ammunition contains lead. Store in a sealed container, wash hands after handling, and dispose of packaging per local hazardous waste guidelines. California Proposition 65 warning applies.
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