Earlier today Say Uncle sent me an email asking if I could help out a reporter looking for “someone of authority” to address the body armor versus deer hunting ammo issue. I know a lot more about exterior ballistics (I wrote Modern Ballistics) than terminal ballistics but I’m not totally ignorant of it either. So I agreed to “look up a few references” for the guy.
My email, with very minor edits, to the reporter follows. His email response indicated he was happy with my answers.
Say Uncle asked that I address your “deer ammo going through body armor” story. I’ll address it as best I can but strictly speaking I’m not an expert. I’m a very well informed hobbyist.
Although there is occasional some controversy over the National Institute of Justice testing procedures and standards they are still “the standard”. You can read their standard here.
Their main page on Body Armor is here.
Probably the part that is most relevant to your issue is the body armor classification. This can be found in section 2 starting on page 17. The basics are that body armor is classified according to the level of protection it provides. Those classes are, in order of increasing protection level:
- Type IIA (9 mm; .40 S&W)
- Type II (9 mm; .357 Magnum)
- Type IIIA (.357 SIG; .44 Magnum)
- Type III (Rifles)
- Type IV (Armor Piercing Rifle)
Most law enforcement officers wear type II or IIIA. Higher levels of protection require metal or ceramic inserts which increase the weight, bulk, and the body heat retention. See also Section 6, Selecting the Appropriate Level of Protection in this document. At some point in the tradeoff between comfort and protection the police officer will stop wearing the armor on an everyday patrol. In a high risk entry/arrest situation they are more likely to upgrade to type III armor if it is available.
The problem certain well intentioned politicians get into is that they don’t realize the body armor problem is as much a velocity problem as it is a bullet construction problem. Certainly sharp pointed Teflon coated tungsten carbide (a very hard metal used for metal working tools) bullets will penetrate a higher level of armor than a blunt nosed soft lead bullet. But that only goes so far. Increasing the velocity of the bullet by a few hundred feet per second will overcome the inferior construction in most applications. Rifle bullets are much faster than common pistol bullets. The typical handgun bullet is on the order of 1000 fps. A typical modern center fire rifle bullet leaves the muzzle at a velocity on the order of 2500 fps or greater.
I’ve done some informal testing with the 30-06 rifle on an engine block. The Speer Reloading Manual says of this rifle cartridge, “It is safe to say that the 30-06 Springfield is the best-known and most successful centerfire cartridge ever developed.” In a typical hunting load (see http://www.federalpremium.com/products/details/rifle.aspx?id=260) at 100 yards from the muzzle the bullet is still traveling at over 2600 fps. The tests I did were with a target cartridge and bullet (http://www.federalpremium.com/products/details/rifle.aspx?id=148). At the muzzle this bullet is traveling at about 2700 fps and is still going at over 2500 fps at 100 yards. I was shooting into the side of a six cylinder car engine from the early fifties from about 50 yards away. This was a very heavy engine block compared to today’s cars yet the target bullet would penetrate half way through the block penetrating the water jacket, one side of a cylinder and frequently one side of a piston. A very high velocity (1350 fps at the muzzle) 9mm bullet shot at the same engine block only knocked the rust off of the metal. It did not dent or crack the side of the engine.
It is a very different problem to stop a rifle bullet than to stop a handgun bullet. Although it isn’t quite this simple you can think of it as an energy problem. The energy of the projectile is proportional to the mass of the bullet times the velocity of the bullet squared. That is E = m V2. The mass of a common hunting bullet is on the order of 150 to 180 grains. The mass of a pistol bullet is on the order of 125 to 200 grains with the heaver bullets moving much slower than the lighter ones. The rifle bullets typically are moving about 2.5 times as fast as the pistol bullets. Hence they will typically have about 2.52 or about 6 times as much energy as the pistol bullet.
Even the ancient 30-30 Winchester cartridge has a muzzle velocity of nearly 2400 fps with a 150 grain bullet (http://www.federalpremium.com/products/details/rifle.aspx?id=28) which will cut through the typical concealable body armor worn by law enforcement on a daily basis. Higher end rifles for larger game such as, the still very common, .300 Winchester Magnum with a 165 grain bullet (http://www.federalpremium.com/products/details/rifle.aspx?id=592) have muzzle velocities of over 3000 fps. Run the numbers on that and see the sort of problem the body armor is facing.
Hence, the NRA claim that outlawing ammunition on the basis of its ability to penetrate typical body armor would result in the banning nearly all common rifle hunting is true. It is possible the politician did not have that intention but that would be the result.
That is probably more information than you really wanted but I hope it answers your questions. If not or if you have any further questions please let me know.