By Shane Foster
Talk about ballistic helmets long enough, and you’re bound to hear terms like “backface deformation,” “resistance to penetration (RTP)” and “V50 ratings.” These have shaped the industry’s idea of helmet performance for years. The problem, however, is that backface deformation, in particular, has become a sacred cow in the industry, despite no hard evidence proving it’s a major cause of fatalities.
Perhaps it’s time to step back and reconsider whether we’ve been focusing on the right things.
A metric in question
Backface deformation (BFD) is the depth of the dent inside a helmet after it’s hit. Industry and medical standards set the danger threshold at anything over one inch (25.4 mm). Even so, real-world evidence raises doubts about whether BFD is the most important factor in survival.
Over the years, I have asked this question to some of the largest police agencies, including New York, Las Vegas, Dallas and more: How many documented cases can you tell me about where somebody died because of backface deformation? The answer is virtually none.
Consider that in 2018, the U.S. Department of Defense (DoD) released a thorough study — without any input from helmet makers — examining 77 helmets damaged by small-arms fire. [1] The results were strikingly clear: Helmets that experienced complete penetration resulted in fatalities nearly three out of every four times. However, helmets that successfully stopped the projectile completely prevented fatalities, with all individuals involved returning to duty with relatively minor injuries.
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For instance, back in 2019, during a mission in Afghanistan, a soldier’s helmet stopped a 7.62 mm round during a firefight. [2] Thanks to that protection, he walked away with only minor bruising. The Army later returned the helmet to him — impact mark still visible — as a powerful reminder of just how critical the right gear can be.
In other words, how many times has backface deformation been the documented reason someone didn’t make it home? The answer is virtually never.
In fact, in all my experience with law enforcement, the only case mentioned involved an officer who was struck, fell and then was struck by a car, making BFD an indirect factor at best.
Of course, BFD remains a key design factor, with some manufacturers achieving an extremely low BFD without sacrificing ballistic integrity. While it isn’t the main cause of fatalities, its mitigation remains important nonetheless for blunt force trauma protection.
Yet, the industry tends to give BFD too much weight. Why? As we’ll see, it’s not because the data backs it up, but because of an attachment to the way things have always been.
Going deeper
Another crucial metric in head protection is V50, which tells us the speed at which a projectile has an even chance of either penetrating or being stopped. There is a common assumption that this metric only measures resistance to military fragments, but in truth, it’s a major factor in determining a helmet’s overall defense. Put simply, a higher V50 rating means better protection against a range of threats, from frags to handguns to rifles.
Notable is that prominent ballistic standards — NIJ, NATO (STANAG 2920) and MIL-STD-662F — each interpret V50 differently, making apples-to-apples comparisons somewhat difficult. Standards don’t guarantee protection of course — what a helmet is made from is critical to its effectiveness. For years, helmets were mainly made from aramid fibers, better known as Kevlar, which offered great protection at the time. But with modern innovations, ultra-high molecular weight polyethylene (UHMWPE) has proven to be an even stronger, more protective alternative.
The future of ballistic protection
Think of UHMWPE as the kind of plastic that makes you rethink what plastic can do. It’s ultra-light but strong, shrugs off impacts and doesn’t wear down easily. You’ll see it in bullet-resistant vests, artificial joints, industrial parts and high-performance sports gear because it’s built to last and resists moisture, chemicals and UV damage.
When it comes to practical performance, UHMWPE leaves Kevlar behind. Polyethylene fibers have a far superior strength-to-weight ratio, being approximately 15 times stronger than steel and twice as strong as Kevlar. In fact, polyethylene outshines Kevlar in more ways than one. It won’t absorb water, won’t degrade from UV exposure, and because it’s less dense than water, helmets made from it are far lighter and more wearable.
The biggest difference, however, between Kevlar and polyethylene becomes obvious under ballistic conditions. Kevlar, as a tightly layered and stitched material, tends to handle slower-moving projectiles well, but as the velocity rises, it can fail suddenly (think of a tennis ball impacting a net that “catches” it as opposed to a window screen that allows the ball to tear straight through). Polyethylene, on the other hand, acts more like an automobile’s crumple zone, absorbing impact forces and preventing penetration more effectively.
Live fire
When evaluating BFD, penetration resistance and V50, there’s a big difference between controlled lab experiments and the kind of real-world trials that tell you how a helmet will perform when it matters most. That’s why Team Wendy coordinated a series of field tests that weren’t just about checking boxes but about putting aramid-based and UHMWPE-based helmets through the kind of punishment they might see in the line of duty.
The tests were conducted by Team Wendy’s product specialists in conjunction with various law enforcement agencies who provided shooters ranging from ballistic testing experts to seasoned tactical professionals; people who know firsthand what it’s like to be in situations where your gear is the only thing standing between you and serious injury. Some had military combat experience, others had spent years in law enforcement tactical units, but they all had the same goal: to find out exactly how these helmets would hold up when pushed to their limits.
When testing gets tactical
To get real answers, the team headed to North Central Texas and other locations. While laboratory testing is crucial to tell the real story of the data, shoots validate these numbers and build confidence among end users that helmets will perform in all types of live-fire situations. That meant shooting these helmets with 9 mm and .40 caliber, then pushing them to the limit with the high-energy impact of .45 ACP and .44 Magnum at close range.
Here’s a breakdown of the rounds used:
- 9 mm (135 grain Critical Duty)
- .38 Special (158 grain Remington)
- .40 caliber (165 grain, ~1,053 fps)
- .45 ACP (230 grain, ~835 fps)
- .44 Magnum (320 grain, ~1,270 fps)
The shooting sequences were uncut, showing the real moment of impact without manipulation — just raw, unfiltered footage of rounds hitting helmets so that law enforcement agencies and industry professionals could see exactly how they performed. And the results spoke volumes.
Time and again, the UHMWPE-based helmets showed minimal backface deformation, usually less than half an inch, and completely stopped penetration, even at high speeds. This became clear in impacts that would have shattered comparable aramid-based helmets. In one test, a UHMWPE-based helmet completely stopped a .45 ACP round with almost no deformation.
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The human factor in helmet design
Once again, the takeaway is that survival isn’t about one metric. The industry needs to take a broader approach to helmet testing — one that stacks the wins across multiple performance categories. The test results provide the data, and the data is validated in the field. That’s to say, a 9 mm-rated helmet is just fine until a rifle round shows up. Development and evaluation need to reflect that reality.
Consider, for instance, that ballistic testing has traditionally used soap and clay head forms, meaning that when a helmet is tested, it’s on a perfectly round head. But no human being has a perfectly round head. That’s what makes us unique. Some heads are very symmetrical, some are egg-shaped — but no two are identical.
In the simplest terms, consider two helmets being struck in precisely the same spot, resulting in 7 mm backface deformation. For one wearer, it can mean a minor headache.
For another, it can lead to potential injury based on the unique head shape. To say it another way, a helmet with a “low BFD” doesn’t automatically mean it will reduce injury for everyone.
Because head shape matters. Skull density matters. Fat content matters. Hydration levels matter. A round peg cannot be forced into a square hole, but testing has taken this approach for too long.
More to know
Of course, a helmet’s job goes beyond just stopping a projectile. It has to offer consistent protection from every angle — front, back, crown and sides — against everything from heavy blows to repeated rapid impacts.
And that protection has to include more than just bullets. Blast overpressure is a real threat, and most helmets weren’t built with it in mind. A 2020 study out of Walter Reed and NJIT took a hard look at what actually happens under the shell when a blast wave hits. [3] Using a highly detailed head form, researchers found something surprising: in certain scenarios, helmets may not reduce pressure — but amplify it, especially around vulnerable areas like the eyes and forehead. The shape of the helmet, the angle of the blast, the padding inside — they all played a role. The takeaway? Some helmets might be doing less to protect against blasts than we think. It’s a wake-up call for the industry to start designing for the full threat picture, not just what shows up on a firing range.
For years, obsessing over narrow benchmarks has led to overlooking broader performance factors critical to real-life scenarios. Threats don’t come in neat, predictable packages. A truly protective helmet must offer consistent, all-angle survivability across a range and duration of threats.
BFD is just one piece of a much larger, more complex puzzle — it’s time to focus on the full scope of ballistic protection. Helmets need to be designed to stop penetration first — because the moment you have a hole in the helmet, nothing else matters.
It’s time for agencies, manufacturers and procurement leaders to take a hard look at what truly saves lives. The data is clear: penetration kills, and helmets that stop penetration — regardless of minor deformation — give wearers a fighting chance to go home.
Decision-makers should revisit their procurement criteria and ask tougher questions about what helmets are actually tested against, and how. Are they built for symmetrical head forms or human variability? Are they tested against the kind of rounds officers and service members actually face? Are we designing to win lab scores or to save lives in the field?
Ultimately, ballistic protection is about trust. And the only way to earn that trust is to test and build helmets like lives depend on it. Because they do.
References
1. Mortlock RF. Protecting American soldiers: the development, testing, and fielding of the Enhanced Combat Helmet (ECH). Project Management Journal. 2018;49(1):6-20.
2. U.S. Army. Army returns life-saving helmet to Soldier, unveils new protective gear. March 7, 2019.
3. Mahajan P, Ganpule S, Przekwas A, Chandra N. Factors contributing to increased blast overpressure inside modern ballistic helmets. Appl Sci. 2020;10(19):6731.
About the author
From the front lines of law enforcement special operations, Shane Foster built his career in law enforcement starting in 2001. He was promoted to sergeant in 2012, but after three years, pivoted to private training while keeping one foot in the field as a reserve deputy and advisor to elite tactical teams.
During his service as an NCO with the 164th Division of the United States, he led FAST missions in support of Operation Inherent Resolve and Operation Freedom’s Sentinel. Today, as Product Specialist Manager at Team Wendy, Foster applies that experience to improving protective helmet technology. He is also the founder of Guild Solutions Group, specializing in CQB and breaching training.
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