The Trouble With Front Face Spall/Splash

Posted: March 6, 2014 in Spall, Spall Guards
Tags: , , , , , , ,

Steel rifle plates have several advantages, especially for certain applications (PSD, concealed). they are the thinnest profile of all rifle plate styles, are generally very inexpensive, do not suffer from fragility issues inherent with ceramic plates, and handle multiple hits extremely well (some plates have been documented with hundreds of rounds while still retaining their protective qualities).

Interior of 6X6 splash guard after M193 3100 fps impact @ 10 feet on AR500 steel side plate. Non penetrating strike.

With all these advantages, there are several drawbacks, the largest and most pressing being that of front face spall (also known as splash). Spall refers to any ejecta resulting from an impact event. Rear face spall has been an issue mainly with tanks/AFVs for as long as they have been used. In WWI, British and German tank crews suffered casualties from rounds impacting the armor and kicking off shards of the plates at high velocity. Even though the rounds may not have penetrated, damage was still done. The British took advantage of the principle of spall with their development of the HESH round after WWII. This was an explosive shell with a soft head, which, when it hit the enemy vehicle, exploded on the outside. The shock wave blew large chunks of spall off the interior of the vehicle.

Front face spall, or splash, is the result of the projectile disintegrating into a cloud of high velocity fragments. The cloud usually manifests as a primary and secondary conoid of splash, the first being made up of the larger jacket pieces. This usually bounces back at an angle very close to the initial strike. The secondary conoid, which makes up about 80% of the total splash threat, travels primarily along the face of the plate, to exit at close to 90 degrees from the original strike. It is this conoid that presents the greatest threat to life and limb.

Because of how steel rifle plates function, this unfortunate property occurs every time a bullet is successfully stopped. Stopping the round is the purpose of the plate, but up until recently, no consideration was given to keeping the face, throat, and extremities safe from the cloud of cutting fragments. Generally, higher velocity rounds produce more spall (the M193 is a more dangerous round for splash than M80 ball, for instance). The core composition will also play a large role in splash/spall. The M855 produces less spall, due to a larger volume of the core being taken up by a mild steel penetrator. The penetrator is fairly easy to trap with spall mitigation technologies. Close range impacts will obviously pose a greater spall/splash risk than longer distance shots.

Early solutions (still used today) involved plastic or elastomer coatings (in some cases, the same materials used as truck bed liners). These coatings range in thickness from fractions of a millimeter, to nearly half an inch. While effective (at least in the thicker iterations), the material is removed by each successive hit, and in the thinner versions, the spall mitigation is very limited. The main drawbacks involve the thickness of effective coating depth, which mitigates the main point of steel plates (their thin profile), the fact that the coating is permanently removed (which is difficult or impossible to replace). Coated plates often have an offensive, strong chemical odor as well. Coating steel plates is not a bad rust-preventative, but the thinnest coating is recommended.

Other, more recent solutions involve adding metallic components to the plate. While undoubtedly effective at catching splash exiting the sides of the plate, adding MORE metal, MORE weight, and MORE thickness to already heavy plates is not an optimal solution.

Some users have attempted various DIY “solutions,” which usually include haphazard combinations of duct tape, epoxy, gorilla glue, woven aramid or UHMWPE, or brush-on truck bed liner. These solutions are a poor choice, tending to turn steel plates into a messy, ugly, smelly, and above all, ineffective mess. The plates will still stop the rounds as usual, but the splash mitigation is negligible. Because the attempts do not take into account the dynamic nature of an impact, the strong adhesion will couple the facing materials to the plate, resulting in very quick erosion of the homemade guards. This, combined with poor choice of materials (woven Kevlar fabric, or UHMWPE laminate) guarantees failure.

Specially designed slip-on guards utilizing custom engineered/manufactured aramid blend fibers have so far proven to be the best combination of attributes for capturing front face splash/spall. These guards can be removed, swapped between plates, or replaced once used, and are thin, light, and above all, COMFORTABLE. They can be built for ANY steel (or ceramic, for that matter) plate currently extant.

Steel plates can be an excellent choice, but it is vital for end users to be aware of potential safety issues. There are several options for mitigating splash, each with their unique benefits and weaknesses. Above all, ensure you are using adequate splash protection if you choose to run steel rifle plates, and keep your face and extremities safe!

https://drmorgear.wordpress.com/products/spall-guards/

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