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The anatomy of a gunshot and why your bullet choices matter

A bullet nerd breaks down bullet testing and what makes some ammunition more effective than others

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The author’s preferred loading for his AR-15 duty rifle is the Gold Dot due to its bonded bullet and consistent quality.

Warren Wilson

By Warren Wilson for Police1 BrandFocus

I’m a bullet nerd. I have been since I was a kid. When the infamous Miami shootout was ended by hero FBI Special Agent Edmundo Mireles, Jr. in 1986, I was 15 years old and read everything I could about it. That event shone light on ammunition effectiveness like no other in history at that point. One of the felons was shot through his upper arm. The bullet entered his torso but failed to penetrate to the vitals. He then went on to kill two agents and seriously wound another.

The caliber, bullet construction and ammunition manufacturer came under tremendous scrutiny after that. Every popular gun magazine of the day had a seemingly endless stream of articles on wound ballistics. I found most of them overly opinionated and underly scientific, even as a teenager. Still, if you go on a gun forum today and title a thread, “9mm v. .45” you’ll start a firestorm.

FBI Protocol

The FBI spent years studying wound ballistics and ammunition effectiveness. The result of those studies was what we commonly call today, “The FBI Protocol.” It is considered to be the standard by which law enforcement ammunition is measured. Testing is conducted in bare 10% ballistic ordnance gelatin as well as eighteen inches behind the following intermediate barriers:

  1. Heavy Clothing – four layers of clothing which is defined down to the thread-per-inch count and type of material.
  2. Steel – 20-gauge, hot rolled steel with galvanized finish set three inches apart.
  3. Wallboard – Two pieces of ½ inch standard gypsum board set 3.5” apart.
  4. Plywood – One piece of ¾ inch fir plywood.
  5. Automobile glass – One piece of 15” x 18” ASI ¼” laminated safety glass set at a 45-degree angle and 15” to the side.

It’s important to understand the FBI requires use of approved, calibrated, organic gel and not the less expensive and easier-to-use clear gel. Our own Mike Wood breaks down why that’s important in this article. Some departments have made poor choices in duty ammunition for lack of understanding the differences in bullet performance in these mediums.


Bare gel upsets for a 9mm HST and G2 load

Vista Outdoors

I don’t think most folks get why we like gelatin testing. Ballistic gelatin is not supposed to be analogous to humans. One inch of penetration in gelatin does not equal one inch of penetration in a human. That’s not the point of gelatin. The point is that it is a medium that in which we can test defensive ammunition and get consistent, “apples to apples” comparisons. The lab guys at Speer and Federal explain it very well here.


G2 and HST upsets sitting on top of bare gel after being shot through it and pulled out to record weight retention and expansion diameter

Vista Outdoors

Jello Junkies vs. Morgue Monsters

Those researchers who favored gelatin testing were labeled “Jello Junkies.” At the same time, “Morgue Monsters” were gathering data on actual shootings. Almost immediately after the first dial-up Internet connection was made in the 90s, message boards, chat rooms and forums were filled with arguments about which method was the most valid and not much has changed as of this writing. Both approaches yielded some good information.

After years of reading all these studies, I could no longer complain about “underly” scientific testing. One of the greatest advances to come from this type of testing and especially barrier testing is bonded bullets. When the jacket of a bullet separates from the core, penetration suffers. Since penetration to the vitals is the most important element of incapacitation and since we commonly face barriers, bonded bullets are a must for law enforcement.

The Anatomy of a Gunshot

There’s more to quality ammunition than the construction of the projectile, though. There are three other components: the casing, primer and gun powder. To fully understand what makes a quality defensive round, we need to know how a cartridge works. The firing pin strikes the primer. The small explosive charge in the primer discharges and lights the gun powder. As the powder burns, gasses expand forcing the bullet down the barrel. If the burn rate of the powder is off, the bullet can be lodged in the barrel or the gun may simply blow up. As the bullet leaves the chamber, it contacts the lands and grooves or rifling in the barrel, causing it to spin. That spin stabilizes the bullet. If the velocity is too low or too high, the bullet won’t stabilize in the air properly, causing it to veer off target.

The primer and primer pocket must mate perfectly. If they don’t, liquids may leak into the cartridge, destabilizing the gun powder. If a primer is ignited without a proper seal, gasses can seep backward into the breech face, causing damage and possibly even injury to the shooter.

Speaking of gun powder, quality manufacturers use a low-flash propellant. That helps the shooter from being distracted or blinded by the muzzle flash during low-light conditions. The brass casing is also a consideration. Duty-quality cartridges should have nickel electroplating. Nickel plating is less porous and therefore more slick than bare brass. That results in more reliable feeding into the chamber and less friction between the fed round and the one below it in the magazine. Nickel plating also provides better corrosion resistance. Those are the standards by which I choose my important ammunition.

HST and Gold Dot

In the early 2000s, because of this self-imposed standard, I made the decision that all my defensive/duty ammo would be either Federal HST or Speer Gold Dot. A long-time friend and I split a 1000-round case of HST. Sometimes, you look back on decisions with regret. I only wish I’d bought more. To this day, I use HST or Gold Dot in every defensive gun I have including 5.56mm. Why did I make that decision? Check out how these rounds perform.

Rangemaster Instructor Conference

I was honored to present at the inaugural Rangemaster Instructor Conference in 2017. John Correia of the wildly popular Active Self Protection YouTube Channel also presented at the conference. He took the opportunity to poll the over 50 instructors in attendance on their choice of defensive ammunition. John referred to us as a “clue-ful” group of folks and I would agree. About three-quarters of us reported carrying either HST or Gold Dot. I’m to the point where it would take a lot for me to justify carrying anything else.

Gold Dot G2

The Gold Dot G2 may just be what does that for me. Instead of a large cavity nose, G2 has a shallow dish filled with high-performance elastomer. On impact, the elastomer is forced into engineered internal fissures to start the expansion process, as opposed to conventional designs that rely on fluid to enter the hollow point and create expansion. That results in more uniform expansion, better separation of petals and more consistent penetration across barrier barriers and velocities. The G2 is making waves and, at present, consistently yields the best results in the FBI protocol of any pistol round.

Conclusive data about ammunition

Today, we have more than enough information to make a conclusion about law enforcement ammunition. The folks at Federal and Speer have found that the gelatin testing parameters they use for testing is backed up by street data they get from law enforcement agencies. These two companies have been our ammunition workhorses for the last few decades, at the very least.

One thing I haven’t mentioned up to this point is cost. Law enforcement pricing for Gold Dot and HST ammunition is consistently lower than any other high-quality ammo geared toward cops. When someone asks me what they should carry for defensive ammo, I have to respond. “Why wouldn’t you carry HST or Gold Dot?”


No matter if you are a fan of 9mm, .40 caliber or .45 ACP, HST and Gold Dot are great choices for defensive ammunition.

Warren Wilson

Warren Wilson is a captain, training commander and rangemaster with an Oklahoma metropolitan police department. He is a former SWAT team leader, current firearms instructor and writer. He is certified as a De-Escalation Instructor and Force Science Analyst by the Force Science Institute. Warren has over 3,100 hours of documented training including multiple instructor certifications on firearms, active shooter and OC. He has been a full-time law enforcement officer since 1996.