15 January 2013

Barriers

This post has been in draft form for a long time.  It really doesn't have much to do with firearms, and more to do with the things to think about when confronted by a barrier.

An ethical hunter will not take an obstructed shot on game.  The rules of good sportsmanship prohibit taking risky shots that might wound and animal. 

A Soldier or even Law Enforcement Officer may need to engage another human being who is using cover or concealment.  Let us define each.

Cover is something that stops the bullets aimed your way.  They might be able to see you (through bulletproof glass or a big block of ice), but they cannot hit you with direct fire.

Concealment simply hides you from direct observation by your opponent.  The enemy can't see you, but if they have enough bullets to shoot through the tin shack or apartment door you will learn the difference between cover and concealment the hard way.

The definitions are fairly simple, but what could be "cover" for a 9x19 could only be "concealment" to a 357 Sig.  In fact this little bit of wisdom is why the Chicago Subway Police are issued firearms in 357 Sig, it can launch a bullet fast enough to penetrate a subway seat with enough terminal velocity remaining to do significant damage to someone behind the seat.

The last few posts in the Firearms Lethality series have dealt with bullet construction and velocity.  Barrier penetration is something that has been touched on with Armor Piercing rifle ammunition and KTW pistol rounds.  The barriers designed to be defeated were made of steel.  But barriers can be anything, from sheetrock to tempered "bulletproof" glass.  The guys at the "Box O' Truth" showed that bulletproof glass really is bulletproof, for a while anyways http://www.theboxotruth.com/docs/bot48.htm.

The truth is that in order to defeat "cover" or a "barrier" all you need is time and ammunition.  I don't want to think about how many 22LR cartridges you would need to defeat NIJ level 3 rifle bulletproof glass.  But you would need significantly less 50 BMG to get the same effect.  Even standard ball 50 BMG would be fine, but specialty rounds are available just for punching through armor steel or bulletproof glass.

But, bullet design is nothing without some terminal velocity bringing kinetic energy into the act of turning cover into concealment.  Toss a rock at a bulletproof glass viewport and you might not even make enough damage to obscure vision, but hit it with a precision 12 gauge slug a couple times and things get interesting to anyone behind the glass.  Conversely, if you don't want to go the "big and slow" route, you can always go with the "screaming fast" method.  These two schools of thought are not mutually exclusive, and so you can get some really screaming tough bullets.  In a low mass, high velocity cartridge like the 5.56x45, making the projectile "tougher" is the easy answer.  If you want to compare two bullets against each other, test them against some barrier and find the "V50" numbers (lower is better).  V50 describes the velocity where 50% of the bullets defeat the armor in question.  http://www.dtic.mil/cgi-bin/GetTRDoc?AD=ADA567525&Location=U2&doc=GetTRDoc.pdf  One should note that using standard M855 or M855A1 bullets in a higher velocity round like the 22-250 or 223 WSM would increase the range at which the bullet would remain "armor piercing."  What exactly that extra velocity would do at closer ranges is beyond my ability to predict, but assuming the bullet can behave as designed, ballistic performance against barriers should be improved.

Now, there are different types of barriers.  Bulletproof glass (and most non-homogenous armor in general) uses alternating layers of hard and soft to redirect, absorb, and disperse the kinetic energy and momentum of the projectile.  Other types of barriers, such as sandbags or snow (do not underestimate the ability of an unpacked snowbank to stop a bullet) simply use a lot of mass to bleed energy and momentum away from the projectile.  Composite materials (carbon fiber reinforced ceramic, resin impregnated aramid fibers, fiberglass reinforced concreate) use a bit of both properties (mass, and multiple materials) in order to spread out the impact to an area larger than the diameter of the projectile.

The hole in a sandbag will be the same size hole as the bullet.  The hole (or impact crater) on bulletproof glass will be orders of magnitude larger than the size of the bullet.  Some materials (like homogenous steel) behave more like sandbags than like bulletproof glass.

In the race between small arms and armor, armor has won.  That is why explosively formed projectiles and warheads have been developed, for everything from Rocket Propelled Grenades to anti tank missiles.  Because in the end, if your small arms fires simply aren't working, several pounds of explosives usually help out quite a bit.

Explosives are a lot like machine guns, if you aren't effective, you need to use more....  And if you always choose the biggest, fastest, toughest thing you have, all that remains is to ensure you have ENOUGH of it to defeat the barrier you want to defeat.

13 comments:

StukaPilot said...

I live in deep Mexifornia. Other day I was in the local gun shop and asked about getting some .308 armor-piercing rounds for my M1a. No joy, was told it's not legal in this state. Did buy some 150-gram "standard military ball" .308. Now I wonder, in case of a 3 AM visit by State Security, what kind of impression - if any - would this loading make on ceramic armor at close-range?

California Midwesterner said...

Stuka--

The only 7.62x51 NATO AP rounds are indeed legally prohibited.
However, M2 AP bullets from .30 ball (i.e. .30-06) are still legal, even here in the People's Republic of Kaliforniastan, to the best of my knowledge. They can be loaded in .308, to similar velocities as their original spec.
That said, good luck finding any in the current panic-buying climate.

As to your second point, Level III NIJ armor (as in SAPI--but not ESAPI--plates) is rated to stop 7.62 NATO/.308 Win Ball at 2780fps, though I don't know offhand how many impacts.
Level IV NIJ armor is rated to stop at least 1 hit of .30 AP at approximately 2800fps. There are multi-hit level III and IV plates out there, too.
Information from Wikipedia here

AM said...

StukaPilot,

If the Zetas come knocking, the hard plates in their body armor will stop anything a 308 can push out.

However, hard points in body armor are inflexible, and pretty much any bullet from a 308 can punch through "soft" body armor.

Make like a sniper and aim for the hips, give the Zetas a bad day. I know of no company that makes hard plates (either ceramic, polymer, or armor steel) specifically for the hip area. Doesn't mean it isn't out there though, but if I were being attacked by the Zetas, that is what I would do.

Anonymous said...

I would presume the Zetas (which in reality will be the second line confiscators) will come in with shields, so go for the feet. Our local cop show a well armed suburbatopia outfits each entrant in 3000 dollars worth of armor, so presume it is way beyond a PC with ceramics for each. A friend of mine suggested Molotovs, but I'm sure the 6 second rule trained entrants go by will negate that option. I suggest pray to Odin and Thor. RRS

riverrider said...

as to your article- thermite. as to the entry team-dotfifty, or multiple 308 hits will set them back on their ass where you can shoot his naked underbelly. THATS why we need 30 rd mags.

Mt Top Patriot said...


Dear AM,

Barriers?

You realize what just happened in NY?

They just shut off the northeast corridor. You can not get in or out of New England with your arms without traveling through NY state.

You see the set up here?

Tactical and strategic choke point. With rolling VIPR teams on the roads they can ambush at will whomever they wish looking for persons, arms, and materiel.

Something you write about often.

NY is a kill zone. A funnel to channel enemies of the state into so they can be picked off piecemeal.

To get those who aren't afraid.

Along with it being an outright strategic act of war on our Liberty to defend from tyranny, a litany of acts of treachery, treason, and tyranny, this is in direct contravention of Article 10 of the US Constitution-Powers Prohibited States. Of course it is in direct violation of the 2nd, 4th, 9th, Amendments.

The ruling class always has others do their dirty work. They are nothing but corrupt windbags without useful tool minions to commit the deeds required to impose their assumed power.

That usually requires participation of armed forces in some manner when the serfs revolt.

Something already in place.

As these acts of tyranny escalate, a breaking point approaches. The blood is going to run. Lots of it. So when the dot mil gets called out by the elites to reinforce the enforcers because a bunch of deer hunters hand them their traitor arses and whittle down their numbers, what are you going to do?

I'll tell you what I'm going to do AM.
I'm going to fight like a cornered animal. I'm going to fight to win. I'm going to exact a comeuppance that will chill the blood of the elites.

When you get called up to carry arms and enforce diktat on American soil, against sovereign Americans, what are you going to do AM?

When it is marshal law, by name or not. What are you going to do AM?

This goes far past that Oath I keep asking you about.

Mt Top Patriot said...

PS,

“A man must stand for something or else he shall fall for anything.”

AM said...

Mt Top Patriot,

I've been thinking about the situation in New York. When I have thought enough I may even write about the situation.

However, the Firearm Owner's Protection Act has a "safe passage" clause, even though New York has refused to honor it in the past.

Anonymous said...

Some years ago, some associates and I hosted a group of video game developers at one of our little get-togethers. They were working on a FPS and wanted to get weapons effects dialed in. We demonstrated M1, M1919, M1 SMG, MG42 and 34, MP40 and StG44. We shot at 55-gallon drums, cinder blocks, a section of brick wall we had built for the occasion, a small earthen berm, and we hung whole briskets in the trees. To say they were horrified at the effects of the 1919 would be putting it mildly. Brick wall you're hiding behind? Stops the first 10-20 rounds, by round 50 in the belt, wall is GONE, and you've already soaked up so much spall you don't really care anymore. The berm only buys you time to get lower in your hole or leave out the comms trench. The brisket shoot turned some of them green. They were most concerned that they would now have to design and program dynamic terrain and obstructions that would keep track of how much and by what they had been shot with so that they would degrade appropriately.

pdxr13 said...

Anon- re. "video game" or simulators:

So, this is why I need an 8-core Xeon and 4 SLI-linked graphics cards with space-heater-like output when graphics options are turned up high in modern 1st person 3-d programs?

AM: What I take from this article is that man-made "barriers" are, in most cases, a delay for a team with enough ammo/demo capability, even when defended. This seems a testimonial for thick and very-heavy (& cheap) compressed earth block construction as opposed to transparent-to-projectiles wood-frame construction.

More fundamentals: being under siege in a static position sucks. Fire and maneuver makes the enemy try to find you while you find them, as well as bringing new barriers between you and their fires.
As a person who lives somewhere, it seems that I would be unable to build a fortress/bunker system capable of defeating a Zeta team who might be equipped with drones and indirect fire weapons, but a certain amount of hardening may buy time to retaliate, call for help, or depart. A certain amount of body armor and vehicle armor may do the same.

Availability of ammo: poor, especially for the "standard" types like 5.56NATO/7.62SOV/12ga defensive/.22LR. Plenty of target/game birdshot that won't cycle a Saiga. Bubba and his brothers have bunches of weapons and decided that having only a box of ammo for each was insufficient, just like 2008, so they call-in their 401K/IRA money for something real. Expect another quarter of very good financial results from arms and ammo mfg's.

Cheers.

Anonymous said...

I've got to get through that barrier this spring-relocating. Best I can come up with is FFL arms home and surface transport the rest. Ideally commercial carrier.....to the north Canada, to the south, ocean.....
yeah I already know New England is not the place to be, but it's home......Can anyone speak to the Safe passage clause?

10mm AUTO said...

Mt Patriot,

You're White. Most of New England is White, therefore you are the Enemy, the "bitter Clinger", the hated WASP, the blue eyed Devil of Farrakhan, Rev. Wright, Dr. Cone and the rest. Of course you are cut off. If there is resistance to the FEDGov, then roadblocks will be installed "for Safety" searching for guns, Gold, alcohol, etc. Anything that might hurt the resistance will be done. The evil White male is the worst and until you realize it and are willing to shoot back or print some leaflets or plant some Semtex, you are being herded to the mass grave like sheep.

Anonymous said...

"(do not underestimate the ability of an unpacked snowbank to stop a bullet)"

indeed.

astonishing how many projectiles (esp. 9mm & .223) are found on top of the ground when snow is no more at the local range

and, steel core commie stuff has astonishing penetration in ferrous material