If you carry a 10mm, hunt with a hard-hitting revolver, or want a defensive round that punches above its caliber, you have probably looked hard at Underwood Ammo. The Illinois company built its name on full-power, high-performance loads — the solid-copper Xtreme Penetrator and Xtreme Defender projectiles, hard-cast hunting and bear loads, and one of the deepest 10mm lineups in the business. It is the ammo for shooters who want everything their gun can safely give. Here is who they are, what they make, and what is worth buying.
Who Underwood Ammo is
Underwood Ammo is a Sparta, Illinois company founded in 2013 that makes high-performance, full-power handgun and rifle ammunition — known for its Xtreme Penetrator and Xtreme Defender solid-copper loads, hard-cast hunting ammo, and a deep 10mm lineup, all made in the USA, including the packaging.
The company was founded in 2013 by Kevin Underwood, a competitive target shooter and avid hunter with an engineering background who saw a gap in the market. He wanted ammunition that was faster, cleaner and left less residue — and that delivered honest, full-power performance at a reasonable price. What started as a small operation grew into a respected family-owned business that prioritizes quality over mass production. You can read their story on the Underwood about page.
Underwood is committed to manufacturing 100% of its products in the USA — right down to the packaging — and in 2025 announced a major expansion with a new facility in Georgia. That growth reflects a loyal following among shooters who want loads tuned for maximum effectiveness rather than the lowest possible cost.
On price, Underwood sits in the premium-performance tier. You are not buying bulk plinking ammo; you are buying carefully loaded, often solid-copper or hard-cast rounds designed to do a specific job extremely well. For defense, hunting and big-bore work, that focus is exactly the appeal.
What Underwood Ammo makes
Xtreme Defender and Xtreme Penetrator
These are Underwood’s signature loads. Built around solid-copper, monolithic fluted projectiles (a Lehigh Defense design), the Xtreme Defender creates a wide wound channel without relying on expansion, while the Xtreme Penetrator drives deep — Underwood notes it consistently exceeds 18 inches of penetration for dangerous game. They do not deform or clog, which makes them popular for defense and against tough, bone-heavy targets.
Hard-cast hunting and bear loads
For hunters and the backcountry crowd, Underwood loads heavy coated hard-cast bullets in big-bore calibers like 10mm, .44 Magnum, .45 Colt and .460 S&W. These flat-nose hard-cast loads penetrate straight and deep, which is why they are a go-to choice for bear country and large game.
The 10mm specialty
Underwood is one of the names most associated with serious 10mm Auto ammunition — full-power loads (within SAAMI spec) in JHP, XTP, Xtreme Defender/Penetrator and hard-cast, covering everything from defense to the woods. If you bought a 10mm to use its real potential, this is a first stop.
Defense and range loads across the lineup
Beyond the specialties, Underwood loads conventional JHP and XTP defensive rounds and FMJ across the popular handgun calibers — 9mm, .380 ACP, .38 Special, .357 Magnum, .40 S&W and .45 ACP — plus a growing rifle selection, all nickel-plated brass-cased with quality components.
Build quality and the full-power philosophy
Underwood loads to the top of what a cartridge can safely deliver, using quality components — nickel-plated brass, sealed primers, and premium projectiles like the solid-copper Lehigh designs. Everything is made in the USA and quality-checked rather than mass-produced. The honest trade-off is twofold: these are premium-priced rounds, not bulk range fodder, and because they are loaded to full power, some shooters and some firearms prefer milder ammunition for high-volume practice or older guns. For the shooter who wants maximum real-world performance from defense, hunting and 10mm loads, that full-power approach is the whole point.
How Underwood compares
Underwood’s closest rivals are the other full-power specialists, Buffalo Bore and DoubleTap — all three load hot, hard-hitting ammo for defense and hunting. Underwood generally competes well on price and on its embrace of the solid-copper Lehigh projectiles. Against the big names — Federal, Speer and Hornady — Underwood is the boutique, performance-first alternative: less ubiquitous, but loaded hotter and offering exotic projectiles the majors do not. It also shares DNA with Lehigh Defense, whose projectiles power its Xtreme line.
Be honest about the trade-offs: Underwood is premium-priced and not a bulk plinking brand, and its full-power loads are more than some shooters need for casual range time. If you want the cheapest practice ammo, a bulk brand fits better; if you want the widest retail availability, the majors win. Underwood is for the shooter who prioritizes performance and is willing to pay for it.
Who should buy what
- The 10mm owner: a full-power Underwood 10mm load — XTP for defense, hard-cast for the woods.
- The concealed carrier: an Xtreme Defender in 9mm, .380 or .38 Special for a wide wound channel without relying on expansion.
- The bear-country hiker: heavy coated hard-cast in 10mm, .44 Magnum or .45 Colt.
- The deep-penetration believer: the Xtreme Penetrator for tough, bone-heavy targets.
- The revolver hunter: hard-cast .357, .44 Magnum or .460 loads.
- The performance seeker: any Underwood load when you want the top of what your cartridge can safely deliver.
Who should look elsewhere? If you want cheap, high-volume practice ammo, a bulk FMJ brand is the better value, and shooters with older or lighter-built firearms may prefer standard-pressure loads. Underwood is for defense, hunting and big-bore performance.
The Underwood philosophy
Underwood treats ammunition as a performance product, not a commodity. Founded by an engineer and competitive shooter, the company loads to the honest top end of each cartridge, adopts advanced projectiles like the solid-copper Lehigh designs early, and keeps everything made in America. It is a performance-first, quality-over-quantity mindset, which is why Underwood earned a devoted following among 10mm shooters, hunters and serious defenders.
How to choose your Underwood load
Start with the job. For self-defense, choose an Xtreme Defender (wide wound channel, no expansion needed) or a quality JHP in your carry caliber. For hunting or bear defense, choose heavy coated hard-cast for deep, straight penetration, or the Xtreme Penetrator for the toughest game. For 10mm specifically, decide between XTP/JHP for two-legged threats and hard-cast for the woods. Always confirm the load is appropriate for your specific firearm — Underwood loads to full power, so verify your gun is rated for it, especially with older or lightweight pistols.
The ammo that uses every bit of your cartridge
Most factory ammo plays it safe, leaving performance on the table to keep costs down and cover the widest range of guns. Underwood took the opposite path: load each cartridge to the honest top of its potential, use the best projectiles available, and make it all in America. That is why a 10mm loaded by Underwood feels like a different cartridge than the bargain stuff, and why hunters and defenders who care about terminal performance keep coming back. When you want your gun to do everything it was designed to do, Underwood is the answer.
Shop Underwood Ammo & Prices
Live Underwood products and current prices, organized by caliber and updated automatically.
Underwood 10mm Auto Ammo
Underwood 9mm Ammo
Underwood .38 Special & .357 Magnum Ammo
Underwood .45 ACP Ammo
Underwood .380 ACP Ammo
Where Underwood Fits in Our Buying Guides
Underwood Ammo FAQ
Where is Underwood Ammo based?
Underwood Ammo is based in Sparta, Illinois, where it was founded in 2013 by Kevin Underwood. It manufactures 100% of its products in the USA and is expanding with a new Georgia facility.
What is Underwood Ammo known for?
High-performance, full-power loads — especially its solid-copper Xtreme Defender and Xtreme Penetrator rounds, hard-cast hunting and bear loads, and a deep 10mm Auto lineup.
What is the difference between Xtreme Defender and Xtreme Penetrator?
Both use solid-copper monolithic fluted projectiles. The Xtreme Defender is tuned for a wide wound channel for self-defense, while the Xtreme Penetrator is designed for maximum depth, consistently exceeding 18 inches for dangerous game.
Is Underwood 10mm +P?
Underwood’s 10mm loads are full-power but stay within SAAMI specifications and are not +P rated. They deliver the cartridge’s real potential while remaining within spec — always confirm your pistol is in good condition and rated for full-power 10mm.
Is Underwood good for bear defense?
Yes. Its heavy coated hard-cast loads in 10mm, .44 Magnum and .45 Colt are popular bear-country choices for their deep, straight-line penetration.
Why is Underwood more expensive than bulk ammo?
It is a premium-performance brand using quality components and advanced projectiles, loaded in smaller batches and made entirely in the USA. It is defense and hunting ammo, not bulk plinking fodder.
Underwood vs Buffalo Bore or DoubleTap?
All three are full-power specialists. Underwood competes on price and its embrace of solid-copper Lehigh projectiles, with one of the deepest 10mm catalogs. Which you prefer often comes down to the exact load and caliber you need.
What tier is Underwood Ammo?
Premium-performance. Underwood is a US-made, full-power boutique loader focused on defense, hunting and big-bore effectiveness rather than low-cost bulk ammunition.
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