What Thickness of Steel Will Stop a Bullet

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Join Date: Feb 2007

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Ahhh yes, "Steel Targets 101" . . :

Penetration in steel is tied to velocity, MUCH more so than bullet size and weight, and, barring AP or ammo containing steel, even more so than bullet design.

I don't have any formulas, but a .22-250 at 3,600, for example, will "burn" through cold rolled and hot rolled material of 1/2" **easily** at 100 yards and leave deep craters in thicker material, similar to a BB splash in soft mud. I have a piece of iconel that stopped a .22-250 bullet and the mark is a copper-plated crater about 1/2" in diameter and 5/8" deep. A slower bullet, like a .30-06 at 2,900, will often merely dent similar material with no permanent displacement of the surface material. Counter-intuitive, I know, but there it is.

Both cold rolled and hot rolled are typically of rather low carbon, and thus low hardness. While formed steel may be had in certain tempered grades, it is still soft enough to be measured on the "Rockwell" scale. Harder materials are typically measure on the Brinell scale.

To get bullet resistance, it is necessary to go to higher carbon steels, such as "T-1" (long range only) and the "AR" (abrasion resistant) series. The AR series are surface hardened, with a "skin" layer hard enough to require hardness testing in the "Brinell" scale. AR400 has a surface hardness "approaching" 400 on the Brinell scale. AR500 has a surface hardness of 430 Brinell *minimum*.

Assuming a thickness of 3/8" or better, T-1 will still crater at closer ranges/higher velocities, but is considerably more resistant than the average roll-formed types. A buddy used to use T1, but after trying the AR500, he realized he was wasting his money on "expendable" T1 plate.

While AR400 will resist cratering better yet, it will still sustain permanent damage when faced with higher velocity loads, and/or when thinner sections are used. I would only use AR400 in the thicker sections, and the added cost of this extra weight/thickness will negate the savings of buying the lesser material anyway.

Thus, AR500 is the material of choice for targets, and most commercial steel target makers use AR500 of at least 3/8" and many use 1/2".

I have shot my 3/8" AR500 plates at 50 yards with a .300WinMag and 210 Berger at 2,950 fps with ZERO damage. The bullets disintegrate on impact.

I have shot the same plate at 100 with a .338 Lapua, also with zero *permanent* damage, although the elasticity is being tested enough to flake paint off the back side upon impact. After multiple hits, the plate will become dished slightly, which is repaired by turning it around and shooting some more. Standard lead core bullets go to dust upon impact.

At 1,000 yards, **true lead-core, cupro-nickel jacketed** .50BMG ball rounds leave no permanent damage, but DO dish the plate slightly faster than the .338 Lapua at 100. Again, to correct this, we just flip the plate around and shoot it some more. The energy is about 5,500 to 6,000 ft.lbs. at 1k, so it is not surprising that the steel will yield slightly.

The BIG problem with .50 BMG ball is that it is often found with a sintered core, comprised of a mix of mild steel and lead, and this WILL damage the surface with one hit, and I had a few fuse metal to the surface of the plate and had to be removed with a cold chisel. This event leaves a rough spot the size of a quarter, witch, I assume, will be more vulnerable to undamaged areas.

Another major problem with shooting steel with fifties is that regular ball ammo is typically no more accurate than 1-1/2 moa, and most guys not willing to buy Barnes or Hornady match bullets will shoot black-tip AP ammo with much better results, with accuracy usually around 1 moa.

AP *WILL* mess up your steel. We stuck one in a piece of 1/2" T1 plate at 1,400 yards and I personally found that to be VERY impressive. If it doesn't penetrate the steel, it may damage YOU. There is a VERY cool video online where the AP's steel penetrator core comes **screaming** back to the shooter after impact with a steel target of some sort , perhaps an engine block, a few hundred yards out. It bounced off the dirt a few feet in front of him and cracked him in the hearing protector cup. Any kind of AP is dangerous in that aspect, and the 500+ grain BMG penetrator/core is particularly noteworthy.

Even AR500 is vulnerable to the high velocity thing, and at 50 yards, standard .223/55 grain lead core ball will leave small pockmarks in the surface. These marks are no more than 1/16" across, and only a few thousandths deep, but it IS permanent. I guess that with a gazillion or two hits, it will start to burn through the more heavily damaged areas, but I personally don't worry too much about that. We seldom//never shoot it that close anyway - what's the point?

Any kind of steel in the projo will also pockmark the surface, and one of my smaller pieces has a lot of chips in the surface from 8mm steel jacketed ball at 50 yards. Again, that's awful close to use a rifle on steel and it would take a slew of hits to kill the plate, but damage IS being done.

I have bought several sheets of 3/8" AR500 and cut it up for targets. I also have a store-bought "Popper" of 1/2" AR500.

A water jet or plasma cutter must be used to cut it, preferably a water jet. The reasons for desiring a water jet is that the cuts are much more precise/nicer, and that the plasma cutter kills the temper for about 1/8" margin along the cut. 1/8" is not the end of the world, and all of my targets were cut with a plasma cutter, with the only ill effect being a bullet at close range that nicks the edge of the plate will knock a little chip out.

Cutting with a regular oxy/acetylene torch is unacceptable. This method will not only take a week or two, but the prolonged exposure to the broad heat will kill the temper far into the edge of the sheet.

AR series steel costs about double cold rolled, and is in high demand and difficult to find right now, much being used for skid plates on military vehicles. It is not tough enough to be called "armor", which is another animal entirely. I priced a 4x10 (or 5x8) sheet of 3/8" AR-400 material for Vern at Central VA Tactical a month or so ago and it was over $1,000 delivered to my office, but not cut up. It cost me several bottles of Jack Daniels and a few plasma cutter tips to get mine cut up last time. . .

Steel is sold by the pound, and 3/8" material is about 490# a 4x8 sheet, or 16# per square foot. 1/2" material will be 25% more in cost, and for my use, not enough tougher to be worth it. It is also too damn heavy for me to hump around. Lifting even the 3/8" stuff in and out of my truck bed and running it up the berm at Quantico gets old, and my 24x33 plate is already 85#. . .

If only one or two targets are needed, it is more practical and economical to buy commercial targets. If you want a bunch and have a way to handle and cut a 5x8 piece of steel weighing around 610#, it MAY pay to buy a plate yourself.

If anyone here is truly sincere about wanting a full sheet, I would check pricing for you under my business account with my supplier and we could put it on COD and get it delivered to the east or central MD area, or put it on "Will-Call" for your pickup in Easton.

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What Thickness of Steel Will Stop a Bullet

Source: https://www.mdshooters.com/showthread.php?t=3388

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