The THOR Armor Penetration Algorithm


PDA






481
April 8, 2013, 04:18 PM
Lately, I have been testing out the ability of 7.62x39 ammo to get through mild steel plate and have seen it make it through 1/2" plate (12.7 mm), and on some occasions, when using steel core ammo, through 3/4" (19 mm) mild steel plate at close range.

Being the nerdy, "math-geek" type of shooter that I am, when I stumbled upon the THOR armor penetration algorithm-

Vr = Vi – 10α x hAβ x Mγ x Viδ x (sec Ф)x

-I just had to see how it did when compared to my results.

Using a penetration curve generated by the THOR algorithm, the table predicts the performance of 7.62x39 FMJs against mild steel plate from the muzzle (2330 fps) to 100 yards (2050 fps) and 200 yards (1750 fps) and agrees with a lot of what I have seen so far.

http://i1339.photobucket.com/albums/o710/m831z/THORArmorPenetrationAlgorithm21APRIL1961_17655_image001_zps6ea738f1.gif

So far nothing has gotten through the 3/4" thick mild steel plate beyond 25 yards (~2275 fps) as predicted by the THOR algorithm and at (much) closer ranges, I have seen the round (most of it steel core, not surprisingly) make it through 3/4" mild steel plate.

For the sake of comparison, here is how .50BMG M2AP (even if it is a bit of a stretch with an L/D of ~4.5) fares against both mild steel and rolled homogenous armor (RHA) according to the THOR algorithm-

http://i1339.photobucket.com/albums/o710/m831z/THORArmorPenetrationAlgorithm50BMGRHAvLowCarbSteel_image001_zpsa6969c7d.gif




*A note of caution and my disclaimer: For those contemplating shooting at any steel plate with any firearm- it is extremely dangerous and should not be done at close range without adequate protection. Rifle bullets (and in many cases, pistol bullets) can rebound from the steel plate face with enough velocity to cause serious injury or death. Just because I am silly enough to do so (behind some serious cover- I ain't that crazy!) does not mean that I recommend such behavior. Neither I, nor THR, is responsible for the injury or death of anyone who elects to engage in this dangerous activity. Please don't do it. ;)

If you enjoyed reading about "The THOR Armor Penetration Algorithm" here in TheHighRoad.org archive, you'll LOVE our community. Come join TheHighRoad.org today for the full version!
joeschmoe
April 8, 2013, 04:20 PM
In what application is mild steel plate used as armor? None that I can think of.

zhyla
April 8, 2013, 05:35 PM
In what application is mild steel plate used as armor? None that I can think of.

http://softsolder.files.wordpress.com/2009/05/cimg3370-armor-suit-with-bullet-hole.jpg

wally
April 8, 2013, 05:57 PM
Yup, and it wasn't generally effective against the firearms of its era!

PlaneJain
April 8, 2013, 06:11 PM
What is going to keep the bullet fragments from ripping out your throat?

481
April 8, 2013, 07:12 PM
In what application is mild steel plate used as armor? None that I can think of.

The THOR algorithm has available several target material coefficients for the following metals and alloys -magnesium alloy, 2024 T4/T3 aluminum, Ti6Al4V titanium, cast iron, mild steel, RHA, FHA, pure copper, lead, and uranium- some of which are not used for armor. The model is used to evaluate penetration against these alloys, but such evaluation does not imply that they must be used as armor.

The model can also be successfully used to evaluate the terminal performance of projectiles with L/D ≤ 3 against those alloys. The 7.62x39 projectiles that I am using have an L/D of 2.87 (L=0.893"/D=0.311").

If you enjoyed reading about "The THOR Armor Penetration Algorithm" here in TheHighRoad.org archive, you'll LOVE our community. Come join TheHighRoad.org today for the full version!