Armor plate, looking for info

Erik_in_Hoyt · Apr 18, 2009

.308 and 30-06 fmj will drill through 1/2" hot rolled steel.
they will crater 5/8" "tool surface" hardened 4140.
angling your backstop does 2 things: first it increases the cross sectional thickness of the material - which means you can use lighter gauge steel to give an equivalent stopping power as a thicker piece (so at 45 degrees slant, .375" plate will react to the bullet as if it is .5375" thick). Second, putting the steel at an angle to begin with helps "aim" the ricochet, thus lessening your chances of getting hit with a bounce-back.

Hardening the steel makes it more resistant to dimpling or cratering -- which helps keep the ricochet pattern predictable.

SPYDERLK · Apr 18, 2009

Erik_in_Hoyt said:
.308 and 30-06 fmj will drill through 1/2" hot rolled steel.
they will crater 5/8" "tool surface" hardened 4140.
angling your backstop does 2 things: first it increases the cross sectional thickness of the material - which means you can use lighter gauge steel to give an equivalent stopping power as a thicker piece (so at 45 degrees slant, .375" plate will react to the bullet as if it is .5375" thick). Second, putting the steel at an angle to begin with helps "aim" the ricochet, thus lessening your chances of getting hit with a bounce-back.

Hardening the steel makes it more resistant to dimpling or cratering -- which helps keep the ricochet pattern predictable.

Angling does a third thing that is very important... it deflects, rather than stopping the bullet. Much less energy is absorbed by the plate.
larry

xlr82v2 · Apr 19, 2009

I used to shoot IHMSA handgun silhouette, and built a set of swinger targets about 15 years ago from AR400.

As long as you keep your impact velocities down below 2300 fps, the bullets won't penetrate the steel... get much above that, and you'll start to see the bullets crater the steel. The higher the impact velocity, the deeper the crater. Caliber has nothing at all to do with cratering... It's all about impact velocity (Of course, this is limited to non-armor piercing, hunting or target bullets from .224 to .430 caliber... all bets are off if you throw some military AP stuff at it).

Have fun!

Wis Bang · Apr 19, 2009

I helped demo a two lane 'police' practice range in the basement of City hall that was built for pistol practice & qualification.

Each lane had a 4X8X1/2" sheet of plate w/ the bottom on the floor against the back wall and a 1/2" X 6" angle turned to resemble a sideways V supported the top. an additional 2" wide flat section spanned the center seam and each edge. The sandbox was only about 2.5 feet deep so the angle was alot steeper than 45 degrees.

There was a boxed I beam a few feet to the front that kept high shots from going over. The walls were 2" plaster over brick built in the early 20's w/ no additional protection for stray shots!

After tearing down the interior wall I can see why sledge hammers just bounced off & we had to borrow some 'shorti' 45LB jackhammers from the water dept & hold them across our chests & let them hammer away to get the bricks apart...they city was doing this on the cheap using 3 college kids on winter break @ min wage [early 70's a whopping $@.50/hr!] as they had spent millions on the new police facility behind city hall.

The holding cells were behind the backstop...prisoners had little to fear...

It was hard plate 'cause after 50 years of use w/ .38s the main impact area was only scarred a little! My father used to shoot w/ them and they used mostly lead wadcutters.