Backface Deformation, What is it and Why is it Important?

Backface Deformation, What is it and Why is it Important?

Backface deformation is a term you might have heard before, but do you know what it means? Over the years, we’ve come to find out that those wearing body armor don’t, which tells us, they probably don’t know the significance of it, either. In this article, we’ll be answering the questions, what is backface deformation, and how it affects the body.

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What is Backface Deformation?

We’ve hit on it in a few of our previous blogs, most recently in What to do When Shot While Wearing Body Armor, but we’ve yet to go into detail. In simple terms, backface deformation refers to the backside of the plate, where the bullet is caught and prevented from exiting and penetrating your body; it’s the indent caused. 

When you’re shot, the backface is deformed. But how much deformation is an important consideration, because greater deformation means more trauma.


ShotStop®’s Duritium® Ultra High Molecular Weight Polyethylene or UHMWP is constructed in alternating proprietary unidirectional layering. This is different from weaving a bunch of fabric together. UHWMP’s construction makes it much stronger and more effective and helps better absorb the bullet’s kinetic energy very efficiently, which means there’s less backface deformation or less of an indent.

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If you’ve ever shot a firearm, you know the bullet has a lot of energy behind it. That energy translates from speed and mass, which translates into deeper penetration. Creating a material that has significant backface deformation means that energy will cause the body armor itself to indent into the body of the operator further. Material lessening backface deformation means there will be less of an indent in your body armor, and therefore into your body.

“Let’s just imagine taking a steel plate and taking a hammer and putting this on somebody’s torso, and I smash them in their chest with a hammer. What happens to the energy? Let’s do the same thing with the ceramic plate, and let’s do the same thing with a polyethylene plate. Think about what happens with that kinetic energy and what would that do.”

-Skip Gavorski, Business Development, ShotStop®

UHMWP works by use of high modulus fibers with unusually strong tensile strength. Those fibers prevent or create less backface deformation, which means the bullet’s energy is defused and dispursed much more efficiently by the plate system compared to other rifle plate technologies like ceramic or steel.

Backface Deformation Testing

When it comes to body armor, there’s a lot of testing that should go with it if they’re a reputable company, especially if they’re claiming to prevent backface deformation. One of the many tests is for backface deformation. The Standard Test Method for Resistance to Penetration and Backface Deformation for Ballistic-Resistant Torso Body Armor and Shoot Packs falls under ASTM E3017-17a.

ASTM E3107-17A

ASTM has standardized the testing method for all companies who are saying they prevent penetration and backface deformation. ASTM standardized testing for soft body armor, hard plate inserts, In Conjunction With (ICW) body armor, and shoot packs.


The NIJ also has its input on backface deformation.

“There’s a backface deformation allowed [according] to the current NIJ 0101.06 standard [that] allows for a 44mm backface deformation on the first two impacts from these rifle rounds. Then beyond that, stop four more rounds from penetrating. There’s no backface deformation requirement on the last four rounds of the six shots NIJ compliance test.”

-Jason Henkel, Director of Operations, ShotStop® 

Why is Knowing About Backface Deformation Important?

Knowing about backface deformation is important because it can cause trauma to your body. While you’ll probably still walk away with some injuries, you’re still walking away. Without some form of ballistic protection on, if you’re shot, the bullet is going to penetrate your body, and a bruise or broken bones is better than not coming home to your family ever again. 

However, the less backface deformation your body armor has, the better. 

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Think of it this way. Let’s say I am driving at a high rate of speed, and my brakes give out as I’m driving into the parking lot of a convenience store. Which would be better, me going through the front door and not stopping until I hit the back wall or my bumper simply breaking the front entrance, and I come to a stop? 

Suppose you’re the store owner; the less damage, the better. Breaking a door down is a lot less damaging than driving my car through the entire store, knocking shelves down, ruining merchandise, etc.; backface deformation is quite similar. 

If you’re wearing body armor rated for the ballistic you’re shot with, then that armor should stop the bullet from penetrating your skin. However, the armor itself is going to be deformed and press into your body. It can either have minimal backface deformation, where the bullet only slightly deforms the armor, and maybe you end up with a bruise. Or, there can be a significant level of backface deformation, and you end up with a broken rib. 


In a previous webinar, which we transcribed into a blog, we answered questions about body armor, specifically those relating to how helpful or harmful body armor can be. And our experts busted a few common body armor myths

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One of the questions asked during the Q&A was, “Given that the armor stops the round, what other kinds of injuries can be suffered, such as broken ribs, etc.?”

“The injuries that happen from it depends on where it hit the body, obviously. 

...if you get hit with an M80 or 762×51, you are likely to have some broken ribs or worse. Keep in mind; the human heart is roughly ~44mm in from the chest surface; we are told that this is why NIJ backface allowance is 44mm. Bottom line, there’s going to be some backface injury—ballistics [are] a strange thing. I’ve heard stories of bullets hitting people’s calves and exploding their heart because of the blood pressure... AP [Armor Piercing] round hit in front of a body, the entire back can be black and blue of that person, from head to foot. It does very strange things, that kinetic energy, dispersing through the body. It depends on the round; it depends on the angle that that round hit. Many things can happen, including death, even if the plate performs perfectly.” 



If you’re shot, you’re likely going to sustain some type of injury, even while wearing body armor. As Jason said, ballistics can be strange when it comes to kinetic energy and how it’s dispersed throughout your body. 

“It’s bizarre what happens with ballistics because it’s such complex math. Just know that injuries do happen when you get struck by a rifle round especially. Rifle plates dramatically mitigate the risk of death, obviously.”


For those considering bullet-resistant body armor, you should be aware of its backface deformation, as it too can cause trauma to the body: the less backface deformation, the less trauma, the more backface deformation, the more trauma. 

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When you shop for rifle plates, be sure you ask for the backface deformation test results for the specific plate you are looking at. If the company doesn’t want to share that information with you, this should be a huge red flag. ShotStop® is very transparent with our test results (both backface deformation and V50 results from 3rd party accredited ballistics lab NTS.

If you’re looking for quality body armor that’s both lightweight and comfortable, and has a low backface deformation, check out our level 4 body armor. And if you have any questions, don’t hesitate to email us at

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