The good folks at Diamondback Firearms were kind enough to provide me with a loaner DB15P for review so it would just be "wrong" if I didn't sneak in a few terminal tests as I was writing up my review of the pistol. Ideally, I would have liked to test a few more varieties of ammunition through the pistol, but my time with the DB15P has gone by far too quickly and I only managed to squeeze in three terminal tests while I had it.
Keeping with the short barrel theme of most of my terminal testing, the DB15P fit right in with a 7.5 inch barrel. There isn't anything special about the specific loads I tested other than they are all 55 grains and well suited for the 1:9 rate of twist barrel. I was really interested in seeing what level of terminal performance we would get with such a short barrel. The 223 Remington SAAMI test barrel is 24" long. Our test pistol was less than a third that length.
Step 1) Measure and record temperature and relative humidity.
Step 2) Run a 5 shot velocity average over a ProChrono Digital Chronograph at a distance of 10 feet.
Step 3) Run bare gel test shot into a block of Clear Ballistics Gel that is calibrated to 10% Ordnance Gel density. Shot distance is 10 yards.
Step 4) Repeat steps 2 and 3 for each tested load.
Step 5) Run a 600 fps calibration test bb shot into the Clear Ballistics gel block and record penetration depth.
Video Documentation of the Entire Tests from Range to Bullet Recovery:
Hornady ZombieMax 55 grain Z-MAX
Hornady TAP 55 grain GMX Barrier
Speer Gold Dot 55 grain GDSP
My Thoughts on This Test:
As I mentioned in the introduction for this test, I just chose loads at random for testing. Sometimes I get lucky and end up discovering some new insights from the testing. This was one of those cases when luck was on my side.
The bullet loaded in the Hornady ZMAX is actually a 55 Hornady VMAX (varmint bullet) with the red tip replaced with a zombie green tip. Varmint bullets are typically designed for long range shooting and feature a thinner jacket to facilitate expansion. In this test, the bullet performed perfectly with violent expansion and reasonable penetration. Some fragmentation was evident, but I think it was minimized by the relatively slow impact velocity.
Hornady's TAP Barrier GMX was a terminal performance disappointment at first glance because both test shots exited the gel block. This solid copper hollow point is designed to expand. I can only surmise that the velocity generated was not sufficient to cause bullet upset and expansion. On the other hand, we ended up with two virtually identical terminal results showing what happens to a 55 grain bullet that does not expand. When I reviewed the block I remembered seeing the 7.62x39 Wound Profile illustrations from Dr. Martin L. Fackler. The similarity was uncanny. While this was not an exhaustive test, it does provide some new insight into the yaw pattern of 223 Remington at low velocity.
Speer Gold Dot was the only bonded bullet tested. It isn't a hollow point, but a soft point with just a tiny spot of exposed lead at the tip of the bullet. I expected to see the recovered bullet with a smashed nose and some crush damage. I was really surprised to see the bullet had expanded and 5 symmetrical petals had folded back to the bullet shank. The bullet stopped at a reasonable penetration depth so this test was also a success.
Pick or Pan:
Rather than pick or pan the tested ammunition, I would rather put forth a general comment that reasonable terminal performance can be achieved in a barrel as short as 7.5 inches. To my knowledge, there isn't much terminal performance test data available for short barrel AR-style pistols and rifles. The good news is that three random test choices all performed reasonably well. I wouldn't call any of these tests a failure.
Disclaimer....This test should not be considered an endorsement or recommendation for the product(s) tested. All tests represent actual performance in ballistics testing media. Terminal performance in all other media will show different results. It is up to each individual to make their own personal decision on which specific ammunition to use for their needs. It's also critically important to test any ammo in YOUR SPECIFIC FIREARM before relying on it for any purpose.
Ammunition labeled as +P or +P+ should only be used in firearms that have been certified by the manufacturer as safe for the additional pressures generated by these ammunition types.