TESTED: Hornady Sub-X 190gr 300 Blackout

Hornady’s SUB-X bullets are optimized for expansion at subsonic velocities. How well will these bullets perform for 300 AAC Blackout? That’s the question we’ll answer in this story!


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About Hornady SUB-X Bullets

From the Hornady SUB-X product page:

Reliable subsonic expansion

Sub-X® (Subsonic — eXpanding) bullets deliver big results without a big bang! Designed to provide deep penetration below the speed of sound, Sub-X® features a lead core. Long grooves in its gilding metal jacket combine with its flat profile and the patented Flex Tip® insert within the bullet’s hollowpoint cavity to help it expand reliably at low velocities. Cannelures provide positive case crimp, making Sub-X® ideal for semiautomatic weapons.


Patented Flex Tip® technology aids in expansion at velocities as low as 900 fps.


Meets FBI protocol for terminal ballistic test requirements.


Lead core bullet with cannelured jacket provides positive case crimp for use in semiautomatics.


Designed to fit, feed and function in a variety of firearms, including gas system guns.

Loading Setup and Data

This ammunition was loaded on the Hornady Lock-N-Load AP 5-station progressive reloading press:

For die stations, above we have:

  1. Sizing (expander ball only, new brass)
  2. Priming (bottom), no die used (top)
  3. Powder charge
  4. Bullet seat (I showed at station #5 in the video)
  5. empty

You’ll also want to check out the KMS Squared UFO press light, this thing works GREAT!

Here you can see I’m using an Inline Fabrication Quick Change Ultramount as well!

Load Components and Data

Above: the components used for loads tested in this story:

Load Disclaimer

Use load data at your own risk. Ultimate Reloader is not responsible for errors in load data on this website. Always cross-reference load data with manufacturer’s published data.

300 Blackout Full-Auto AR-15

The rifle used in this story is a “special custom” full-auto AR-15. Note: Ultimate Reloader is a Type 07 Firearms Manufacturer (FFL) and Class 2 SOT, otherwise this would be illegal.

Some information about the rifle follows:


Anderson Manufacturing AR-15 300 Blackout Upper:

  • 16″ Carbine length barrel, 1:8 twist
  • Carbine length gas setup


For this story, I’m using a SilencerCo Hybrid 46 caliber suppressor.

190 grain Match Monster 300 BLK Performance

First up was the 190 Match Monster load which I’ve used previously. This load and bullet is GREAT for shooting steel targets, but I had to know how they would do with ballistics gel.

This load produced an average velocity of 1014.8 feet/sec which is a nice velocity for subsonic scenarios. 

When we went to shoot this load with the ballistics gel, thigs didn’t exactly go as planned! Here’s the shot by shot breakdown:

  • Shot 1: Went through the entire single block (only one setup for this shot)
  • Shot 2: (two blocks) Penetrated first block and part of second block, emerging from top of block
  • Shot 3: (two blocks) Same result as Shot 2, but emerging from the side

I was able to find the bullet from shot 3 laying on the ground- following a path along the ground at the angle which the ballistics gel suggested the bullet was travelling as it exited the gel. Amazing.

As you can see in the picture above, the bullet looked to be in very good condition, the only obvious thing was the rifling marks engraved on the bearing surface of the bullet. A quick test on the scale showed the weight at 190.84 grains, most likely exactly what the bullet weighed before striking the ballistics gel.

190 grain SUB-X 300 BLK Performance

And then came the test I was waiting for! I saw how the Match Master bullets performed in ballistics gel, now to compare with a bullet specifically designed for subsonic expansion: the SUB-X!

This load chronographed FASTER than the Match Master with the same weight (190 grains) and same powder charge (12.0 grains CFE-BLK). Average velocity was measured at 1088.6 feet/sec which is perfect for “max performance *and* subsonic”.

You can see the difference in “wound channel” between the 190 HPBT standard bullet and the Sub-X- it’s pretty dramatic! And here’s the “sonoluminescence” as the cavity collapsed, and before the bullet “bounced back” to its final resting place:

Then came the extraction of the bullet, which penetrated to a depth of 17″ (1″ into the second gel block):

The SUB-X bullet expanded very nicely, with perfect symmetry, and no apparent loss of material:

Here’s how the numbers looked:

  • Base diameter: 0.307″, Expanded diameter: 0.463″ (51% expansion)
  • 187.94 retained weight (99% weight retention)

Now that’s some great performance! I can’t wait to see how these bullets will perform on varmints around the ranch! Would I use this rifle and ammunition for home defense? YES.

A Note about Magazines

There’s one thing about the 300 Blackout that you need to be prepared for: magazines are sometimes an issue. With 300 Blackout cartridges having such a different “profile”, this is not too much of a surprise. I noticed during the filming of the video for this story that the flat-nosed profile of the SUB-X bullets can cause feeding issues with some magazines.

Consider the steel AR-15 magazine here next to a Magpul P-Mag 20, both loaded with SUB-X ammunition:

If you look closely at the front cut, you’ll notice how much lower the cut is on the P-MAG compared to the steel magazine. This helps significantly with feeding. The flat points of the SUB-X bullets can “hit the wall” on magazines without this low cut (as pictured at right). One of the things I’m looking at is Magpul’s “PMAG M3 300 B Magazine” which is optimized for 300 Blackout subsonic cartridges. We’ll have to see if that helps things out at all!

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