Cesiumsponge
Member
Woohoo! I finally got my block of acrylic back from my friend’s vehicle and got a chance to take pictures of it. I thought it was interesting and felt like sharing the results. It is a 3-7/8” wide by 12-1/4” tall by 2-3/4” thick block of cast acrylic I bought off fleabay last year. It used to be about twice as wide but I hacked off a piece for building an audio amplifier.
I'm aware acrylic and polycarbonates are used as bullet resistant materials, but in composite layered structures. However, I had this piece of scrap, solid cast acrylic that was collecting dust so I thought "what the heck!".
Anyhow I shot it with a round of M193…rather XM193PD from Federal Lake City at about 15 yards away with a Bushmaster 16” dissipator carbine just to see what would happen. Unfortunately the block wasn’t wide enough and the stress fractures went all the way through its width and the block fell in two large pieces with a MIA third piece I never recovered. If I had the original wider piece of acrylic, it would be standing on my drawer right now as a piece of “gun art”. Now it’s two dilapidated pieces.
In short, the round was stopped completely within the acrylic block itself on visual inspection. I didn’t melt down the goodies and try retrieving the metal to see what is actually contained within. The crater at the “entry wound” is estimated to be about 4” diameter and 3/4” deep. The bullet broke off at the cannelure into two separate rear/tip pieces as documented in M193 impact tests and the bullet tip fragment is found about ¼” further than the rear fragment.
The tip of the bullet managed to penetrate 1-1/2”, and the fragmented rear traveled 1-1/4” It is clear that the bullet violently decelerated through the acrylic which caused excessive friction, causing visible signs of melted and re-solidified acrylic. Anyone who has worked with acrylic knows how easy it is to overheat and melt the stuff. The rear bullet fragment is completely flattened axially and the lead core has swaged through the opening in the rear of the bullet. The tip fragment is about 45 degrees off axis from a bird’s eye view.
In front of the bullet fragments, following the trajectory of entry, there are deposits of lead splatter and signs of melted acrylic which re-solidified with lead particulate, forming a gray opaque acrylic material that penetrates to about 2-1/8”. I would fathom this was a “heat channel” for lack of a better term where most of the kinetic energy turned into heat. Its where all the gooey crumbly acrylic/lead mess is in highest concentration. The rear of the cast acrylic block shows what one might assume is an exit wound, but since all main fragments of the bullet are present, it would be spalling of acrylic from the kinetic energy release of the bullet upon impact. This has been seen on other hard impact tests where a projectile did not penetrate the test surface completely, but pieces on the surface opposite of the impact had material spall off.
Conclusions? This acrylic block managed to stop the bullet… this time. However I suspect that in the process of splitting in half, that dispersed a quantity of kinetic energy away from penetration aspect and it very well might mean that if I had a wider piece that didn’t split in half, the bullet might have penetrated deeper, or all the way through…or I would get the same results. In this case, the bullet was stopped, but it created some nasty spall at the rear side which probably wouldn’t be nice on bare skin.
Anyhow, I’m not promoting or detracting ballistic properties of cast acrylic as a material. Just merely documenting the results of something I don't get to shoot at often. I don’t want to sound like a Box O Truth copycat, but it sure is fun to shoot stuff, then poke at the results.
I'm aware acrylic and polycarbonates are used as bullet resistant materials, but in composite layered structures. However, I had this piece of scrap, solid cast acrylic that was collecting dust so I thought "what the heck!".
Anyhow I shot it with a round of M193…rather XM193PD from Federal Lake City at about 15 yards away with a Bushmaster 16” dissipator carbine just to see what would happen. Unfortunately the block wasn’t wide enough and the stress fractures went all the way through its width and the block fell in two large pieces with a MIA third piece I never recovered. If I had the original wider piece of acrylic, it would be standing on my drawer right now as a piece of “gun art”. Now it’s two dilapidated pieces.
In short, the round was stopped completely within the acrylic block itself on visual inspection. I didn’t melt down the goodies and try retrieving the metal to see what is actually contained within. The crater at the “entry wound” is estimated to be about 4” diameter and 3/4” deep. The bullet broke off at the cannelure into two separate rear/tip pieces as documented in M193 impact tests and the bullet tip fragment is found about ¼” further than the rear fragment.
The tip of the bullet managed to penetrate 1-1/2”, and the fragmented rear traveled 1-1/4” It is clear that the bullet violently decelerated through the acrylic which caused excessive friction, causing visible signs of melted and re-solidified acrylic. Anyone who has worked with acrylic knows how easy it is to overheat and melt the stuff. The rear bullet fragment is completely flattened axially and the lead core has swaged through the opening in the rear of the bullet. The tip fragment is about 45 degrees off axis from a bird’s eye view.
In front of the bullet fragments, following the trajectory of entry, there are deposits of lead splatter and signs of melted acrylic which re-solidified with lead particulate, forming a gray opaque acrylic material that penetrates to about 2-1/8”. I would fathom this was a “heat channel” for lack of a better term where most of the kinetic energy turned into heat. Its where all the gooey crumbly acrylic/lead mess is in highest concentration. The rear of the cast acrylic block shows what one might assume is an exit wound, but since all main fragments of the bullet are present, it would be spalling of acrylic from the kinetic energy release of the bullet upon impact. This has been seen on other hard impact tests where a projectile did not penetrate the test surface completely, but pieces on the surface opposite of the impact had material spall off.
Conclusions? This acrylic block managed to stop the bullet… this time. However I suspect that in the process of splitting in half, that dispersed a quantity of kinetic energy away from penetration aspect and it very well might mean that if I had a wider piece that didn’t split in half, the bullet might have penetrated deeper, or all the way through…or I would get the same results. In this case, the bullet was stopped, but it created some nasty spall at the rear side which probably wouldn’t be nice on bare skin.
Anyhow, I’m not promoting or detracting ballistic properties of cast acrylic as a material. Just merely documenting the results of something I don't get to shoot at often. I don’t want to sound like a Box O Truth copycat, but it sure is fun to shoot stuff, then poke at the results.
Haven't heard it happen before but I suppose there is the chance. 