Ballistics question

boilermaker

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I have a friend who is installing a 3/8" sheet of steel to the outside of an exterior door. This door itself is 1 1/2" thick. He has already ordered the 3/8" sheet and is having it installed in the next couple days. However he is now thinking he wants to further reinforce the door with another 3/8" sheet. He wants to know if there is a difference in the door's ability to withstand rounds between sandwiching the door between the 2 pieces or mating the 2 pieces together on just one of the sides.

I did not know but figure the NES collective would have thoughts.
 
Not sure, but, I would think the inside would need to be installed in a manner which would make it resistant to being blown off the back of the door by the expanded mass trying to exit. Also the hinge system would need upgrad fro additional weight. What is the rear of the structure made of? It would defeat the purpose of a "bulletproof" door if it were typical wood and 2x4s with windows etc.
 
3/4" mild steel will stop everything even 30-06AP for a single shot in one place. 3/8" will not. M855 will occasionally punch through 3/8" at close range.

If he's going to use two 3/8 sheets, tell him to put a 1/2" piece of wood between the two. It will allow the bullet to expand further, lowering the point stress.

That will be a heavy door. The hinges and wall will need to be built accordingly.
 
As with all kinetic energy penetrators the physics of stopping the projectile involve either degrading or deflecting the projectile so that the energy is not concentrated in the tip. Adding a layer of ceramic material sandwiched in between two steel plates is enough to completely shatter rounds that travel at subsonic velocities while supersonic KE penetrators will be degraded by abrasion significantly. So like xtry mentioned above, adding a layer of a different kind of material and some air space between the plates is ideal. By using this methodology, you can use thinner plates and still stop rounds efficiently. Hell Dyneema bullet resist material is super lightweight and can probably be very cost effective compared to a huge piece of 3/4" steel.

Take a look here: http://www.bulldogdirect.com/armorpanels/architectural
 
Is your friend a drug dealer? JK

I would say sandwich the door. If it penetrates the first plate the core will allow for expansion meaning less energy in the impact of the 2nd plate. However the 2nd shot in the same spot might go through.
 
why shoot into a door? don't most people stand on the side of the door to peek out? Last I checked, police- swat -people stack on the side( ply board and drywall always stop bullets in the movies

That thing is going to weight quite a bit. He'll probably need some custom hinges or commercial grade.
 
You know what I do when I start thinking about beefing up my door? Think about how easy a window or wall is to go thru. But if your talking about a hardened safe room then absolutely sandwich it and fill the 2-3 inch core with granite counter scraps and a rubber horse mat. I could rely on a door like that...
 
If he's going to use two 3/8 sheets, tell him to put a 1/2" piece of wood between the two. It will allow the bullet to expand further, lowering the point stress.

So with this logic, it is better to sandwich the door between the two, assuming he was not to add the 1/2" piece of wood? That effectively the door would aid in allowing the bullet to expand further.

I am not sure how far along he is in the project other than he has ordered 1 sheet of 3/8" steel so not sure if he would change directions in materials used at this point. And my understanding is the door frame has been restructed to handle the significant additional weight
 
So with this logic, it is better to sandwich the door between the two, assuming he was not to add the 1/2" piece of wood? That effectively the door would aid in allowing the bullet to expand further.

I am not sure how far along he is in the project other than he has ordered 1 sheet of 3/8" steel so not sure if he would change directions in materials used at this point. And my understanding is the door frame has been restructed to handle the significant additional weight

Yes.
 
Is your friend a drug dealer? JK

drug dealers should prob be more concerned about a police raid, which means reinforcing the entry way to prevent entry. Bars, reinforcing the door frame, etc. all prove effective should you want to delay a SWAT team making entry.

The thing is, like others have stated, how good is the security elsewhere in the structure? You're only as secure as your weakest link.
 
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