Underwood Ammo

Underwood Ammo is the hot rod shop of the ammunition world. While Federal and Hornady load to conservative velocities that work in every gun made since 1950, Underwood loads to the ragged edge of SAAMI pressure limits.

Founded in the early 2010s, this boutique manufacturer built its reputation doing what the big companies won't -- loading ammunition to maximum pressures with premium projectiles. Their 9mm +P pushes 1,300 fps. Their 10mm actually loads to 10mm velocities, not .40 S&W lite like most brands. Their .357 Magnum delivers what the cartridge was designed to do.

If you want maximum ballistic performance from your cartridge, Underwood is the only major brand that actually delivers it. Just make sure your gun is in good condition first.

The company made its name loading cartridges the way they were originally designed, before lawyers got involved. Their partnership with Lehigh Defense created the Xtreme Defender line -- solid copper bullets that don't expand but create wound channels through fluid dynamics.

The Xtreme Defender is what gets people talking. Instead of expanding like a traditional hollow point, the fluted solid copper bullet creates a wound channel through fluid dynamics. No petals to clog on clothing or barriers -- it just punches through and does its job.

• •Wound mechanism comparison: Traditional JHP vs. Xtreme Defender technology

That 10mm difference matters.

Most manufacturers load their '10mm Auto' to glorified .40 S&W velocities because they're worried about liability. Underwood loads 10mm the way Jeff Cooper intended.

180 grains at 1,300 fps or 200 grains of hard cast at 1,250 fps is what the cartridge was designed for.

Underwood applies the same maximum-pressure philosophy to rifle cartridges, though the gains are less dramatic than with handgun rounds.

Popular rifle offerings include:

• •.223/5.56 NATO
• •.308 Winchester
• •.300 Blackout
• •6.5 Creedmoor

Their .300 Blackout loads are particularly well-regarded -- the 220-grain subsonic stays subsonic and cycles reliably, while their supersonic loads push velocity harder than most factory ammunition.

The company focuses on premium bullets and consistent quality rather than trying to cover every possible cartridge and bullet weight combination.

• •Underwood Xtreme Defender vs. mainstream defensive ammo (9mm +P):

The Xtreme Defender's wound mechanism is genuinely different. Traditional hollow points rely on expansion to create tissue damage. The fluted solid copper bullet creates cavitation through fluid dynamics -- think of it as a permanent cavitation channel rather than temporary expansion.

Law enforcement hasn't adopted Underwood en masse, which means less real-world data compared to Federal HST or Speer Gold Dot. That doesn't make it ineffective, but it's worth considering.

Underwood ammunition serves specific high-performance niches where maximum velocity matters.

• •Primary use cases for Underwood's maximum-pressure ammunition philosophy

• •Self-defense shooting: The 90-grain Xtreme Defender in 9mm +P delivers barrier-blind performance at high velocity. Benefits include:

• •Barrier-blind performance at high velocity
• •No clogging concerns with heavy clothing
• •Consistent penetration through car doors

• •Bear country: Underwood's hard cast loads are the standard for revolver-carrying bear guides. The .44 Magnum 305-grain hard cast delivers 24+ inches of penetration in gel -- what you need for large predators.

• •True 10mm power: If you bought a 10mm for serious work, you need Underwood ammunition. Their loads actually deliver 10mm performance instead of downloaded .40 S&W velocities.

• •Full-power magnums: Want to know what .357 Magnum was supposed to do? Underwood's 158-grain JHP at 1,500 fps shows you. Most factory loads are downloaded to 1,200-1,250 fps.

Underwood ammunition costs 50-100% more than major brand defensive ammo. You're paying for maximum performance and boutique production runs.

The enhanced pressures mean your firearm needs to be in good condition. Don't run hot ammunition through a gun with questionable timing or worn parts. Modern guns in good shape handle it fine -- Underwood loads to SAAMI maximums, not over them.

Availability can be spotty. Boutique manufacturers don't have the production capacity of Federal or Winchester. When popular loads sell out, they stay out of stock for weeks.

Underwood Ammo does what the big companies won't -- they load ammunition to its full potential instead of playing it safe with lawyers.

Their 10mm is the only factory 10mm that's actually 10mm. Every other manufacturer downloads it to .40 S&W velocities and calls it good. If you carry a 10mm Glock in bear country, you need Underwood ammo or you're wasting your time.

The Xtreme Defender is interesting technology. Solid copper bullets that create wound channels through fluid dynamics instead of expansion -- it's barrier-blind and won't clog like traditional hollow points. But here's the thing: Federal HST and Speer Gold Dot have decades of real-world law enforcement data. Underwood has gel tests and testimonials.

For most people carrying 9mm in populated areas, HST or Gold Dot makes more sense. Proven track record, better availability, similar terminal performance.

At $1.25-$1.50 per round, this isn't range ammo. You buy two boxes for your carry gun and train with something cheaper. But when you need your ammunition to perform at the edge of what's possible, Underwood delivers what everyone else is afraid to load.

For bear country, rural carry, or anyone who wants absolute maximum performance from their cartridge? Underwood is the only game in town.

• •Federal HST Ammunition
• •Speer Gold Dot
• •10mm Auto Cartridge Guide
• •Bear Defense Ammunition