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Posted: 7/1/2007 4:54:31 PM EDT
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It is dark now, but I will post a photo or 2 tomorrow. Today at the informal range (AKA sandpit) I had my RRA tactical entry carbine, along with some standard issue LC NATO FMJ 55 grain ammo. I also had some steel core LC NATO surplus. Accompanying all of this were 3 steel plates, 3/16ths, 1/4th, and 1/2 inch thick. The standard FMJ around lead pierced both the 3/16ths and the 1/4 inch steel. It only put a moderate dent into the 1/2 inch plate. In comparison, the steel core ammo also pierced the first 2 but not the 1/2 inch. But it did dig very deep into the 1/2 inch steel, resulting in steel deformity where the exit hole would be, something the FMJ could not do. There isn't much difference, unless you consider that it is a safe bet to assume that the FMJ ammo pretty much vaporized when it penetrated the steel, while the steel core probably had a solid chunk of metal capable of further travel and injury or damage to a target. I should probably set up some paper beyond further plates of steel to see if this idea is fact or not. What I need is a 3/8ths plate, as I believe this ammo is rated to penetrate through it. I am wondering at what thickness the standard issue ammo won't go through, but the steel core will. Your comments and experiences are welcome, 'specially those of you with more experience at these sort of things than I. |
I've seen it. I actually read all of it, but it has been updated some since my last read. I however don't remember seeing damage of M193 versus M855 after a penetration through steel. I skimmed through it again just a minute ago and still didn't see it. If it is infact there, could you point it out to us? Thanks, -X |
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The 62 grain projectile used in the M855 round is NOT armor piercing. The steel insert is there for two things: to add mass to the bullet and alter the center of mass of the bullet. This does two things we want: it gives the bullet more mass which means more inertia, so it will travel farther, and it moves the CM of the bullet aft so that it stays pointed forward longer through more air/obstacles than the 55 gr bullet. The real terminal ballistic effect of the steel insert is to ensure that on medium transition (as in penetrating a soft target), the bullet will immediately tumble because its CM is so far back. When the bullet penetrates ANY new medium, it will be disturbed in flight, and punching through a couple of sheets of steel will definitely soak up enough energy to go along with that yaw so that the bullet dented the third plate pretty good-because that's all the energy that was left in it. In contrast, the 55 grain bullet broke up and had little retained mass (and little retained energy) when what was left of it hit the last plate. Remember that the NATO standard is to simply penetrate a "standard NATO steel helmet" at 600m, not to go through anything more robust than that. |
I've seen various posted weights for the insert-one I see a lot is 7gr. Hmmm... just exactly the difference in mass between the original 55 gr bullet and the 62 gr bullet... Coincidence? Probably not. What source was the bullet you took apart? |
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Took longer to get the time to do this. Below is 1/4 steel plate, entrance holes. The 3 on the left are the steel core LC stuff, the other 5 standard FMJ LC. What word am I looking for? Both rounds blast out and leave in place metal "petals". Note the copper jacket actually left embedded into one of the FMJ entrance holes. http://i17.photobucket.com/albums/b51/Geoff40/QuarterEnt.jpg Below is 1/4 inch exit. Not much else to add to what is above, except again the flower petal look to the steel core exit holes while the FMJ exit holes are almost flush with the surface of the plate. Does this show us that the FMJ is pretty much vapor at this point, while the steel core is not? I'm not sure. http://i17.photobucket.com/albums/b51/Geoff40/QuarterExit.jpg Below is the 1/2 inch plate. This is confusing, but I think in part it is because while the plate was being brazed to the beam, the heat acted to harden the steel inconsistantly along the weld. http://i17.photobucket.com/albums/b51/Geoff40/HalfEnt1.jpg (Above) Here are 4 impacts by FMJ rounds. The damage is not consistant. As you can see there is some flower petal effect happening with the FMJ this time. Below are 3 steel core impacts. 2 of these penetrate deep, leaving a protrusion on the back of the plate. The shot on the top right I think nearly did have enough to exit, there appears to be a part of a steel core ebedded deep in to the plate, something not well seen in the photo. I think the bottom right round hit a spot hardened a great deal by the heat, thus the lack of damage. The backside of the plate in this spot has a big splotch of brazing rod welding the 2 pieces together, so the heat was direct. Also note it is right beside a saw cut, another high temp to the steel. Its the only explaination for this lack of damage by steel core I can think of. http://i17.photobucket.com/albums/b51/Geoff40/HalfEnt.jpg The whole 1/2" plate. http://i17.photobucket.com/albums/b51/Geoff40/Half1.jpg |
LC M855 98 lot got from police trade in back in 2001 when YOU COULDNT FIND M855 I wiegh it on my DILLON digital scale its a good scale Ive took apart SEVERAL types of SS109,M855,M193 to compare wieghts of powder,Brass, Bullet etc! I have a list some place I have shot win M855 at 50 yards the steel plate MUST BE SOFT because the M855 went threw it plate was close to 1/2 inch |
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