Monday, November 1, 2021

Steel Armor and Spalling

    I recently came across an article at Guns America with the title, "Steel Body Armor Torture Test: Are Budget Steel Plates Worth the Risk?" and written by Mitchell Graff. The author recounts how his first set of rifle plates were AR500  Level 3+ Multi-Curve plates with the FragLock Build-Up coating to prevent spalling. The author recently purchased ceramic plates to replace the AR500 plates, and so he decided to test the latter; or, more specifically, to test the anti-spalling coating since he didn't use anything in his test that was capable of getting through the steel plate.

    Spalling (or fragmentation) occurs when the bullet strikes a hard surface (like the steel armor plate) that it cannot penetrate and throws up fragments of the jacket and other pieces of metal from the bullet (the lead core can actually liquify and then spray off the plate). If you have used steel plates for targets, you are probably already familiar with spalling as it can imbed sharp pieces of copper jacket in the wood frame of a target holder, and leave a line in the ground below the target where the ground has been peppered with shrapnel. As Graff relates, "These fragments still have enough mass and are moving at a high enough velocity to cause serious secondhand damage to any body parts that stick past the front face of the plate such as your arms, legs, and head."

    Graff decided to do a torture test of his coated steel armor to see how well the anti-spalling coating held up, using a variety of ammunition including .22 LR, 9 mm, various .223/5.56 loads, a FMJ .308 load, buckshot, and .300 Win. Mag. He has a video of his testing and results (see above), but sums it up in his article:

    The build-up coating completely captured the spalling from one round of the 22lr, 9mm, and 223. Every round after those would further erode the bonding surface between the steel and the FragLock Build-Up coat letting some spalling out instead of fully capturing it. The trick to this build-up coat is the ability to capture spalling while maintaining a good surface bond to the steel. Every round passes through this build-up coat and fragments on the steel in a circular splatter pattern tearing the build-up coat from the surface of the plate until eventually, the whole coating will come off. Once the coating is no longer bonded to the surface of the steel plate, all fragmentation is deflected along the same plane as the outward-facing surface of your plate, impacting all surrounding areas. I give a recap of this and start showing it at minute 12:08 in the video.

    To be honest I was surprised how well the FragLock Build-Up coat from AR500 Armor worked. I was expecting 223 to fragment and breakthrough but it was mostly captured for the first couple rounds. This coating even mostly captured all the fragments from 149 grains of 308 when it was hit. ...

Sounds like the spall coating did what it was supposed to do, safely absorbing fragmentation from multiple hits. 

    But the Graff was unsatisfied, writing: 

However, while steel is “multi-hit” capable, it is only as good as the coating applied to stop fragmentation. Otherwise, you are just carrying around a heavy steel plate the deflects incoming bullets from your organs to your legs, arms, and head. Without a heavy and durable build-up coat, all other steel plates will deflect fragmentation straight into your body and should be avoided at all costs. I would rather not have any plates at all and remain more mobile than to be carrying steel plates that deflect any incoming rounds into other parts of my body rather than fully capturing the fragmentation caused by the impact like ceramic plates, or this build-up coating was designed to do.

This seems an unfair and unrealistic conclusion. Based on testing I've seen, ceramic armor will start to fail after 5 or 6 hits from 5.56 Greentip. But it is also recognized that if you are taking multiple torso hits like that, you have more serious problems than your armor. The same applies to the spalling coating on steel armor. Rocky Mountain Readiness has an article about videos that try to scare people away from buying steel armor based on spalling, which points out:

However, there does come a point where the spalling may cause any coating to detach or “delaminate” from the plate. This is usually in the case of the plate being shot 20+ times. Let’s be real, this is not a likely scenario in the least. However, you’ll see some videos on the internet using it as another scare tactic. Again, in real life the body armor is tightly contained inside a plate carrier which means that the coating will continue to do its job even if it lifts up slightly from the plate. Some trolls will point to this and say, “look, I told you so!”. This completely ignores the fact that a steel body armor plate can defeat 20+ shots from a rifle, whereas the ceramic body armor they are touting could handle significantly fewer shots before beginning to crack apart and fail. Not to mention the high incidence of blunt force trauma from ceramic body armor. So essentially, you don’t have to worry about fragmentation from ceramic plates if you get shot 20 times…because you’re most likely dead anyways.

If you are concerned about spalling, there are numerous companies that sell "spall bags"--basically Kevlar liners designed to catch the fragments from a hit on the armor plate. 

    In any event, actual spall coating from a reputable company should hold up well enough. The fact that you could shoot at a steel plate all day without penetrating it is worth something if you are intending to use the armor in a drawn out SHTF situation. Get some spall bags if you are concerned about the coating eventually coming off, although it seems pretty optimistic that you would survive that many armed encounters.

    The real considerations should be weighting durability, cost, and weight (i.e., mobility). I struck a middle ground by purchasing a polyethylene-ceramic layered plate. It is not as durable as steel, but much lighter; more durable than ceramic, but about twice as heavy per plate; and the cost was not much more than steel plates. 

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