Archive for the 'Ammunition' Category



AR-15 Ammunition And Barrel Twist Rate

BY Herschel Smith
3 days, 23 hours ago

There are a lot of articles and discussion forum threads on barrel twist rate for AR-15s.  So why am I writing one?  Well, some of the information on the web is very wrong.  Additionally, this closes out comment threads we’ve had here touching on this topic, EMail exchanges I’ve had with readers, and personal conversations I’ve had with shooters and friends about this subject.  It’s natural to put this down in case anyone else can benefit from the information.  Or you may not benefit at all.  That’s up to you.

This is a discussion about 5.56mm ammunition and barrel twist rates (and later, about the shooter and ammunition quality).  If you wish to debate the effectiveness of the 5.56mm round generally, or wish to disparage the choice of the Eugene Stoner system, I’m sure there are forums for you.  This is not it.

In the real world, ammunition isn’t concentric, and even if it is almost precisely concentric, pour density can be slightly different throughout the ball, and voids can develop.  This causes gyroscopic stability problems with bullets, even in the best manufactured ammunition. But much ammunition would not be considered the “best manufactured ammunition.”  Ammunition will only be as good as the QA under which it was made.

When center of gravity is off-axis it can cause bullet lateral throwoff, yaw and a host of other problems with bullet trajectory.  In order to overcome these problems, rifling twist achieves this gyroscopic stability for the bullet, thus negating the effects of the manufacturing process (at least in part).

Overstabilization can occur with a barrel twist rate that is too high.  There are incorrect commentaries out there on this subject.  This writer explains that higher twist rate is virtually always better.

Conventional wisdom taught us that slower twist rates wouldn’t properly-stabilize a bullet, causing it to yaw. On the other hand, faster rates could over-stabilize lighter bullets, causing similar problems. This is correct in theory—however, modern ballisticians have pretty much de-bunked the over-stabilization theory as a practical matter. All things being equal, it is better to have too much twist than not enough.

While his statement is a bit imprecise, there is something very precise about it.  It is precisely wrong.  Yet there are much cleaner and simpler explanations of why high twist rate is not always good.  One commenter at this discussion thread summed it up well.

You can certainly overstablilze (sic) a bullet if you spin it so fast it doesn’t nose over at the top of its trajectory … Best thing to do is not spin bullets any faster than what’s needed for best accuracy.

Correct.  If a bullet is overstabilized, it tends to stay pointed along its axis of rotation, even on the final (downward) part of its trajectory.  This can cause keyholing, odd aerodynamic effects (flying sideways through the air) and even bullets to wildly spin off trajectory.

Above it was noted that displaced CoG can cause gyroscopic stability problems, including “lateral throw-off.”  This figure is given to us by Paul Weinacht in his paper for the U.S. Army (Army Research Laboratory, ARL-TR-3015) entitled Prediction of Projectile Performance, Stability, and Free-Flight Motion Using Computational Fluid Dynamics (Figure 9).

Angular_Motion_Epicycle

Or if you wish to visualize what this might look like in 3D … Dean and LaFontaine, Small Caliber Lethality: 5.56mm Performance in Close Quarters Battle.

Yaw

Bullets from rifled barrels eventually achieve stability by yawing back and forth, while undergoing a larger revolution about the major axis of the trajectory.  So quite obviously, it’s necessary to spin the bullet, and to spin it enough to give it stability, while protecting the need to nose over on the final part of its trajectory.  Getting this twist rate and spin right has been a matter of much testing, internet fights, and lot of engineering study and heavy spending by the taxpayers.  I know that my guns perform well, and so I decided to contact my manufacturer for his opinion on the matter.

In the interest of full disclosure, I have two Rock River Arms rifles, one Elite CAR A4 with a 16″ Barrel, twist 1:9, Quad Rail, and another competition gun with a muzzle brake and 18″ SS barrel with a twist rate = 1:8.  I have recommended RRA rifles to my readers before, but there are many good guns on the market.  Your probably have one.  I sent a list of three questions to RRA, and Steve gave me these responses (the question isn’t included because it wasn’t forwarded back to me, but it’s apparent what I asked except for the first question, which was basically does RRA warranty their 1 MOA for both M193 and M855.  This is Steve’s response.

Herschel,

Thanks for your questions.  I’m going to take them in reverse order.

3.  1:9 is adequate for many, but not all rounds typically used in an AR platform.  Between .223 Remington and 5.56mm NATO, there are rounds from 45 to 90 grains (that I am familiar with) and I know of, but have never shot, lighter and heavier rounds.  No single twist is going to handle all of them.  1:9 is adequate for a sizable number of them, however…including the two most commonly available, in bulk and at reasonable prices…55gr FMJ (M193)and 62/63gr FMJ (M855).  It is not ideal for rounds lighter than 50gr nor those over 68 or 69 grains, which is why there are other twist rates commonly available…including from RRA. We offer a 1:12 24” bull barrel for our Varmint hunters who prefer to use the lighter bullets for prairie dogs and other targets, and both 1:7 and 1:8 barrels in a variety of configurations for those who want to shoot heavier bullets…up to and including the newer 77gr loads and 80gr VLDs.  We’ve also run custom twists for a limited number of contracted purchases.

2.  Yes.  1:9 does well with both M193 and M855.  Different barrels perform differently, but 1:9 generally stabilizes both weight/length bullets fairly well,  It neither over nor under spins either and does not produce key holing.

1.  The hardest question to answer.  Neither M193 nor M855 are notoriously accurate rounds.  They meet military, not match, requirements.  Our accuracy claims are the rifle’s capability…but the shooter and ammo have to do their parts.  There are loads that are commercially available and claimed to be “M193” and “M855” equivalents that clearly aren’t, and they aren’t  capable of  ”minute of bad guy” at 100 yards, let alone the .75 to 1.5 MOA claims that we make for our different rifles.  That is no reflection on our rifles or barrels, or the shooters…unfortunately there is some real crappy ammo on the market today, which will not perform well out of any barrel, of any twist rate.

Thanks.

Steve/RRA

This is a good response, but let’s not stop here.  While perhaps not recalled by some, American Rifleman has given us a fairly comprehensive look at 5.56mm ammunition and barrel twist rates in an article entitled Testing The Army’s M855A1 Standard Ball Cartridge.  It is rich with history on how the Army fielded the M855A1.  Ignore the issue of the M855 versus the M855A1 for a moment and consider the background.

Accuracy cannot be assessed without addressing the rifle barrels’ twist-rates. In the early 1980s the M855’s 62-grain bullet was developed for the M249 Squad Automatic Weapon (SAW). For purposes of interoperability, the same load was adopted as the M16A2 rifle’s standard ball as well. A February 1986 U.S. Army study noted that the M855’s bullet required a “1:9 twist [which] would be more appropriate for the M16A2 rifle, improving accuracy and reliability.” Multiple studies confirmed the 1:9-inch twist requirement.

But then a problem arose. The U.S. military’s standard M856 5.56 mm tracer round was longer, heavier (63.7 grains) and slower than the M855 ball, and simply would not stabilize with a 1:9-inch twist barrel. Thus, despite it doubling M855 group sizes, the M16A2 (and later, the M4) specified a 1:7-inch rate-of-twist barrel to stabilize the tracer round. It remains so to this day. Therefore, M855A1 was test-fired with both 1:7- and 1:9-inch twist barrels, and it was verified that this new cartridge is consistently more accurate in the latter barrels-as was its predecessor.

Don’t slip past these paragraphs, because they explain why “Milspec” is 1:7.  It isn’t because 1:7 shoots M193 or M855 more accurately.  It’s because of the weight of tracer rounds.  As we’ve discussed before, the term Milspec doesn’t mean better, or worse, or anything at all except that it precisely meets the specifications outlined in the purchase order(s), excepting whatever variance notifications they might make on a given batch of guns.

The M855A1’s developers have described it as yielding “match-like” accuracy, which most rifle shooters would define as one minute-of-angle (m.o.a.), or groups measuring no more than 1 inch at 100 yards. While the new ammunition has proved more accurate than the green-tipped load it replaced, testing did not yield match-like accuracy, especially in the standard 1:7-inch twist-rate found in today’s M4s and M16s. At 100 yards, the best group with a 1:7-inch barrel was 1.62 inches (1.6 m.o.a.). At 300 yards. it similarly fired 1.6 m.o.a. (4.9 inches) and widened to 1.8 m.o.a. (7.5 inches) at 400 yards. At these same distances, firing the M855A1 through a 1:9-inch twist barrel reduced group sizes by approximately half.

The tests demonstrated that 1:9 twist produced better accuracy, approximately twice as accurate.  Now take note what the testers found with the newer M855A1 regarding repeatability.

On average, the new ammunition produced one flyer in roughly each five rounds, which, it can be argued, exaggerated the group sizes. Since the Army announced that, “On average, 95 percent of the [M855A1] rounds will hit an 8×8-inch target at 600 meters,” each group’s most errant bullet impact was discarded and group sizes recalculated. Statistically they improved, but not enough to place 95 percent of rounds so close at 600 meters, at least when using the standard 1:7-inch barrel-which may explain why accuracy was less than expected.

There is one “flyer” in every five rounds.  This seems to me to be a significant problem with this ammunition combined with the barrel twist, and the commenters don’t seem to like it very much either.  Finally, this.

When U.S. Army shooters twice fired public demonstrations of the new round, they did not employ standard 1:7-inch twist M16A2s or M4s, but accurized, match-grade, stainless-barreled rifles from the Army Marksmanship Unit (AMU). I contacted the AMU and learned that these rifles did not have standard-issue 1:7-inch barrels, but most likely 1:8-inch twist, which probably accounts for their “match-like” accuracy.

Isn’t that rich?  The Army made claims of “match-like accuracy,” and proved the rounds shooting out of different barrels than are deployed with Soldiers, using 1:8 twist, not 1:7 twist.

The American Rifleman article goes on to discuss in some detail the performance of the M855A1 with slim-profiled targets like malnourished tribal fighters in Afghanistan (so-called “ice picking” the target without fragmentation), performance at barrier penetration (concluding that it is better than its predecessor), and its lethality once it does penetrate barriers.  I recommend this reading to you.  It’s well worth the time.

So to summarize what we know, remember some basic things.  First, the bullet has to be spun to give it gyroscopic stability.  This spin needs to match the bullet (including mass and length), and care must be taken not to over-stabilize the bullet.  If you shoot typical .223 ammunition (55 gr.), or M193 or M855, a twist rate of 1:9 is probably just about ideal.  You’ll probably lose some accuracy with a higher twist rate.

This loss of accuracy is likely not significant for a lot of shooters.  If you shoot much heavier ammunition (and there is a lot on the market), you probably need to consider a twist rate of 1:8.  Finally, none of this matches the value of good ammunition or good shooting.

That’s the good news.  Most guns can outperform the shooter, and I know that’s the case with me.  I’m a decent shooter.  Not great, but decent.  I’ve taken my Tikka T3 .270 bolt action rifle and literally put rounds through the same hole at 100 yards (with slightly more tearing of the same hole in the paper).  On the other hand, this is with a good scope, no wind, a cool and comfortable day, all day to work my craft and thus no time pressure, no one else to be concerned about, lots of coffee to wake up, and a full belly.

But if I had kept records, it wouldn’t have happened again exactly like that since, theoretically, even with perfect ammunition, considering barrel harmonics and that physical processes like this are a heuristic phenomenon, if I had continued to log my shots this way, it would have doubtless shown a standard distribution (distance between each shot and mean).

But regardless of the details, you’ve done it before.  Control breathing … get good sight picture … back out of the shot if you’re not mentally right … know where your trigger breaks … and so on.  You know the drill, since you’ve done it many times.  It’s perhaps the purest pleasure a shooter can have.

Now throw in simple annoyances like a whining partner at the range, losing daylight and time pressures, hunger, and any of the other 100 possible nuisances that can sap your accuracy.  Then your accuracy goes to hell, doesn’t it?  Now, combine that with wearing heavy gear and being shot at, and I’m sure it diminishes your control over your weapon.  Thankfully, I only have the experiences of my former Marine son conveyed to me.

The good part of this is that regardless of your barrel twist rate, if your AR-15 is reliable, even if it’s not top of the line, it can probably outperform you.  That means getting better isn’t a matter of getting a new rifle or barrel with a different twist.  It means practicing with your rifle, sometimes under duress.  It also means buying good ammunition.  Steve at RRA is right.  The shooter and ammo have to do their part.  I object to cheap ammunition just like I object to cheap engine oil.  I’m trying to develop the discipline at the store or online to buy better ammunition.

Right, I’ve got it.  I feel your objection.  Good ammunition (e.g., Hornady $2 per round .270 for my Tikka) hurts.  This is my wealth, and it’s hard to part ways with it since it’s hard to earn it.  But using bad ammunition at the range makes it hard to impossible to assess your practice.  Use of my value pack Federal .223 at the range means that my accuracy is irrelevant if I’m using the same reticle holdovers I would for 5.56mm since the muzzle velocity is different (and very slightly lower than the 5.56mm).  You’ve got the picture.

The best way to get better accuracy is probably not to get a better gun.  It’s to practice with the one you’ve got.

Here is a related video I found interesting on gyroscopic stability.  He’s wrong about the math being incomprehensible, but it is rather difficult if you’re involved with partial differentials or worse, the Navier-Stokes equations in CFD.  You need some specialized training in mathematics in order to tackle that.  You don’t have to know any of that in order to understand the basics of shooting.

This discussion probably won’t end the debate on barrel twist rate, and it certainly won’t end the fight between the Army and Marine Corps (who doesn’t want to deploy the M855A1).  But I hope it was helpful to you.

Prior:

Considerations In Selecting AR-15 Ammunition

Army And Marines In No Rush To Chamber A Common 5.56mm Round

A New Cartridge For The Army?

Army And Marine Corps On M855 Ammunition

AR-15 Animation

Why I Abandoned The AR-15

Does AR-15 Barrel Length Matter?

$3000 Versus $1000 AR-15

Eugene Stoner And Jim Sullivan On AR-15 Engineering And Design

What Length AR-15 Barrel?

Considerations In Selecting AR-15 Ammunition

BY Herschel Smith
2 months ago

We have previously discussed the Marine Corps battle with the Army and Congress over fielding a different ammunition than the Army, who spent a wad of money on an “environmentally friendly” lead-free cartridge, the M855A1.

Currently, the Marine Corps is trending towards the MK 318, which appears to be a far superior round, and it comes in right at 2900 FPS out of the M4 barrel, higher for longer barrels.  The claim is that it behaves better at longer distances and retains its ability to penetrate.

This trend towards heavier rounds has been going on for some time now, and 62 grains isn’t the top weight for the 5.56mm bullet.  One reader sends information about Sierra 77 grain, and tells me that the 1:9 twist is just fine with this ammunition.  Of course, one gives up something to get something.  In the case of heavier bullets, you give up muzzle velocity.

This velocity detriment may seem small.  TFB likes the Sierra 77 grain, and informs us that its muzzle velocity comes in somewhere between 2500 FPS and 2600 FPS.  But your choice of ammunition will depend upon your target, its distance, any interstitial shielding, potential body armor, etc.

You may do better with M193 than with either the MK 318 or the Sierra 77 grain.  Sometimes the smaller rounds with the higher muzzle velocity are what’s needed to penetrate any armor.  Do you not believe me?  Consider what we learned with the FN 5.7 and its test against bulletproof glass, which only the .454 Casull could penetrate.  The open tip 5.7 round at 22 grains penetrated the glass due to high muzzle velocity, whereas the heavier 5.7 round did not.

Do you need more evidence?  Very well.  Consider that AR500.com sells hard plates it calls Level III, and those plates are rated to stop M855 (steel core) but cannot stop M193.  They have to move up to what they call Level III+ to perform effectively against the M193 due to its higher muzzle velocity compared to the M855.  There’s nothing wrong with having a safe full of M193.

Army And Marines In No Rush To Chamber A Common 5.56mm Round

BY Herschel Smith
2 months, 1 week ago

Military.com:

So it doesn’t seem that the Army or the Marine Corps are in any hurry to explain to Congress why they don’t use a common 5.56mm round.

The final joint version of the Fiscal 2017 National Defense Appropriations Act includes a provision requiring the secretary of defense to submit a report to the House and Senate Armed Services Committees explaining why the two services are using different types of 5.56 mm ammunition for their M16A4 rifles and M4 carbines.

The bill has already passed the House and is expected to be voted on and approved by the Senate this week before going to President Obama’s desk for his signature.

This is not the first time Congress has gotten its dander up over this subject. Lawmakers asked both services to explain the same thing last year, but Marine Corps leaders said they need to do more testing of the Army’s M855A1 enhanced 5.56mm round.

I reached out to the Marine Corps yesterday and the Army today to ask about how they planned to deal with the request. I could almost hear the head-scratching as if neither service had heard anything about it.

According to the provision, the report must be submitted within 180 days after the bill, which includes the entire defense budget for the coming year, is enacted.

If the secretary of defense does not determine that an “emergency” requires the Army and Marine Corps to use the two different types of rifle ammo, they must begin using a common 5.56mm round within a year after the bill is passed, it states.

OK so here is the back story for those you out there who don’t know it.

The Army replaced the Cold-War era M855 5.56mm round in 2010 with its new M855A1 enhanced performance round, the end result of more than a decade of work to develop a lead-free round.

The M855A1 features a steel penetrator on top of a solid copper slug, making it is more dependable than the current M855, Army officials have maintained. It delivers consistent performance at all distances and performed better than the current-issue 7.62mm round against hardened steel targets in testing, Army officials maintain. It penetrates 3/8s-inch-thick steel at ranges approaching 400 meters, tripling the performance of the M855.

The Marine Corps had planned to field an earlier version of the Army’s M855A1 until the program suffered a major setback in August 2009, when testing revealed that the bismuth-tin slug proved to be sensitive to heat which affected the trajectory or intended flight path.

The setback prompted Marine officials to stay with the current M855 round as well as start using the MK 318 Special Operations Science and Technology round developed by U.S. Special Operations Command instead. Commonly known as SOST ammo, the bullet isn’t environmentally friendly, but it offered the Corps a better bullet after the Army’s M855A1 round failed.

Since then the Marine Corps has purchased millions of MK 318 rounds.

The MK 318 bullet weighs 62 grains and has a lead core with a solid copper shank. It uses an open-tip match round design common with sniper ammunition. It stays on target through windshields and car doors better than conventional M855 ammo.

The Army quickly replaced the bismuth-tin slug in its new round with a copper one, solving the bullet’s problems in 2010, Army officials said.

The new Army round also weighs 62 grains and has a 19-grain steel penetrator tip, 9 grains heavier than the tip on old M855 ammo. Seated behind the penetrator is a solid copper slug. The M855A1 consistently penetrates battlefield barriers such as windshields more effectively than the M855, Army officials contend.

The accuracy of the MK 318 may not be what it’s cracked up to be.  However, for any of these heavier than 55 grain rounds, there is a detriment in muzzle velocity (these rounds lose up to 200 FPS), and that can actually make a difference in penetrating capability.

Suffice it to say that creation of an environmentally friendly round for the armed forces is laughable, and the main thing to be concerned about is ballistics.  It would be interesting if someone still in the service would weigh in on this debate.

But as for Congress being briefed on the details of the ammunition being chosen by the armed forces, I agree with one of the comments.  You may as well try to teach physics to a pig.

A New Cartridge For The Army?

BY Herschel Smith
4 months, 2 weeks ago

Popular Mechanics:

Defense contractor Textron just unveiled a new rifle at the Modern Day Marine conference. Designed to use so-called “telescoped” ammunition, the new rifle promises a harder-hitting, lighter bullet for America’s ground troops to fire. Whether the U.S. military is ready to embrace all the change a new rifle and ammunition would bring remains to be seen.

Traditional bullet cartridges have a bullet seated roughly halfway inside a brass shell casing, with gunpowder inside the casing. By contrast, the new rifle uses a 6.5-millimeter polymer-cased telescoped bullet. Telescoped rounds feature a bullet completely encased in a polymer shell, like a shotgun, with gunpowder surrounding the bullet in the shell.

The result is a cartridge that doesn’t use brass, a considerable savings in weight. According the Kit Up! blog, telescoped ammunition is about 40 percent lighter than traditional ammunition. Textron could have channeled this weight savings into making lighter ammunition, but instead it chose to make new ammunition that packs a bigger punch. The rifle—and 20 rounds of ammunition—weighs a total of 9.7 pounds. By contrast, the standard M4A1 (pictured above) and 30 rounds of ammunition weigh 8.74 pounds.

Textron claims the new 6.5-millimeter round has 300 percent more energy than the standard U.S. Army bullet, the M855A1. That translates into greater knockdown power against human targets, more armor penetration, and longer range. A heavier bullet and more energy would solve a persistent complaint about the U.S. Army’s M4A1 carbine—that the smaller 5.56-millimeter bullet often requires multiple hits to incapacitate a target and it lacks the range to make accurate long-range shots. The latter has been a particular complaint in Afghanistan, where long-range engagements are common.

Textron’s rifle is a gas-operated, piston-driven rifle that has many familiar features drawn from the M4A1, including a charging handle and gas block. It features military-standard rails for the attachment of devices such as flashlights and lasers, and what appears to be Advanced Armament Corporation flash hider. The front and rear sights, pistol grip, and buttstock are all from firearm accessory manufacturer Magpul.

Well, whatever.  It isn’t clear why the round has more energy.  That could be due to greater bullet mass or bullet velocity or a combination of both.  The mass of the bullet, grains of powder, muzzle velocity and other information are left unsaid.

If it has a higher muzzle velocity, then that will come with side effects such as shooting the barrel rifling out sooner than with the M4.  I could be wrong and commenters may correct me, but my understanding is that the guys who shoot .243 in competition have to be sponsored due to having to change barrels out so frequently (at 4000 FPS the barrels are good for only several hundred rounds and then they have to be replaced to maintain accuracy).

If the bullet has more mass along with more powder to propel it the same velocity as the 5.56 mm (~ 3150 FPS), then it has more recoil which will cause a change in the ability of the shooter to retain sight picture (a huge advantage of the low recoil 5.56 mm).  You don’t get something for nothing.

The 5.56 mm round has ended the lives of many enemy fighters in Vietnam, Iraq and Afghanistan.  It has a long history of being a highly proficient round, and most complaints about its effectiveness are due to the inability to properly utilize it.

I’ll stick with the Stoner design, thank you.  If the new cartridge is worth anything, it’ll have to prove its mettle in battle.

 

5.56x45mm Versus 7.62x39mm

BY Herschel Smith
1 year, 2 months ago

The never-ending caliber debate can be tiresome, but then again occasionally there are good and useful additions to the body of knowledge.  Because of my son being deployed, I have always known and understood (not first hand, but second hand) the utility and superior performance of the 5.56mm in the field (and when I say “field,” I mean Fallujah, not your local shooting range where your know-nothing, tacticool weekend warrior waxes stupid in front of everyone).

I have also heard from his teammates about being shot by the 7.62×39.  Specifically, Corpsman Prince gave me details of his experience.

He was very kind and friendly, well trained, in excellent physical condition, and had absolute commitment to his fellow Marines.  He showed me his wound from Iraq within several days of returning.  A round from an AK-47 had entered through the front part of his lower thigh, ricocheted up his thigh, and exited out of the very upper part of the back of his thigh.  Entry and exit wounds (now scars) were at least a foot apart.

Corpsman Prince stayed in Iraq and did his own rehabilitation during the deployment.  The hardest thing about the experience, he told me, was getting enough pairs of clothing after each successive pair became blood stained.  The more interesting thing about what happened that day with Corpsman Prince was what happened to his fellow Marines.  He wasn’t the only one who was wounded in that engagement.  Several other Marines were also wounded, and Prince had to treat them before he could treat himself.  He did so while bleeding out.

The exit wound was small, virtually as small as the entry wound (if the scar is any indication of the wound size when it happened).  The scars I saw were identical in size.

But the specific addition I wanted to mention has more authority than anything I can muster.  It comes via Defense Review, from Tacmed Australia.  I will quote at length, and then offer up a disagreement and an agreement.

Admittedly I’d rather not be shot with either, but if I had to choose, I’d take a round from the AK47 over the M4 any day of the week. To understand why, it’s important to have a very basic look at the physics behind terminal ballistics, in this case being the science of what happens when a penetrating missile enters a human body. The first place to start is the Kinetic Energy Equation:

KE = ½ M (V1-V2)2

Breaking this equation down into its components, we have Kinetic Energy (KE) influenced by the Mass (M) of the penetrating missile, as well as the Velocity (V) of the missile. This make sense, and it is logical that a heavier, faster missile is going to do more damage than a lighter, slower missile. What is important to understand is the relative influence that Mass and Velocity have on Kinetic Energy, as this is key to understanding why I’d rather be shot by an AK than an M4. You’ll notice that the Mass component of the KE equation is halved, whereas the Velocity component is squared. For this reason, it is the Velocity of the projectile that has far more bearing on the energy that it dissipates into the target than the mass. The V1-V2 component of the equation takes into consideration that the projectile might actually pass straight through the target, rather than coming to rest in the target. In this instance, the change in the Velocity of the projectile as it passes through the target (V1 being its velocity as it enters, and V2 being velocity on exit) is the factor that is considered when calculating how much energy the missile delivered into the target. Naturally if the projectile comes to rest in the target (ie: no exit wound) then V2 equals zero and the projectile’s velocity as it entered (V1) is used to calculate the KE.

That’s enough physics for now, but you get the concept that the optimum projectile to shoot someone with is one that has a decent mass, is very, very fast, and is guaranteed to come to rest in your target, as to dissipate as much energy as possible into them, and hence do maximal damage.

The next concept to grasp is that of permanent cavitation versus temporary cavitation. Permanent cavitation is the hole that gets left in a target from a projectile punching through it. You can think of it simply like a sharp stick being pushed through a target and leaving a hole the diameter of the stick. The permanent cavity left by a bullet is proportionate to the surface area of the bullet as it passes through the tissue. For instance, if a AK47 round of 7.62mm diameter at its widest point passes cleanly through a target, it will leave a round 7.62mm hole (permanent cavity). If this hole goes through a vital structure in the body then the wound can be fatal, however if the bullet passes through soft tissues only then the permanent cavity can be relatively benign. This is a slight oversimplification of the concept, as bullets will rarely remain dead straight as they pass through human bodies, as they have a tendency to destabalise, and for the heavier back end of the bullet to want to overtake the front. This concept, known as yaw, increases the frontal surface area of the bullet as it passes through tissue, and hence creates a larger permanent cavity.

Here is my disagreement so far.  I’m not certain that the author understands the distinction between cavitation and creating a cavity (or perhaps it is that he isn’t clearly delineating the difference).  Cavitation has to do with the formation of voids due to change of state of a liquid to a gas, whereas some of what he is discussing has to do with the yawing and fragmentation of the 5.56mm round in tissue.  There are both of these effects at work.

We’ve discussed the rocking back and forth in flight that occurs with the 5.56mm round, based on the very well researched paper Small Caliber Lethality: 5.56 mm Performance In Close Quarters Battle.  This rocking back and forth during flight, which occurs even with boat tail 5.56mm, causes rapid yawing when it enters tissue.  Fragmentation ensues, ensuring multiple fragments take different trajectories through tissue.  This may be what the author is referring to when he mentions permanent cavity.  Or then again, he may be referring to the high velocity of the 5.56mm round, and as I said above, both effects are at work.

But by mentioning Newtonian physics, he is on to something.  It’s not only the energy of the projectile that’s important, but the velocity term is a function of the exit velocity, which means that it’s also important how much energy gets deposited in the object.  If the bullet doesn’t stop, fragment, or otherwise leave its energy in the object, it will not do as much damage as one which does.  It’s the same way with, for example, radiation.  A high energy gamma (e.g., from N-16) can pass through a piece of tissue without ever interacting with orbital electrons and ionizing atoms.  Thus, high energy photons can pass through a body without causing dose, depending upon depth, energy, etc.

In order to demonstrate the point, he provides two videos, one of 5.56mm in ballistic gelatin, and one of 7.62 in ballistic gelatin.  But the most impressive thing the author does is convey his own experience treating wounds from 7.62 mm and 5.56 mm rounds, and then show you what an X-ray looks like of an upper thigh and femur that has been hit with a 5.56 mm round from a couple of hundred meters.

5.56mm_X-Ray_TacMed_Australia

As I said, this was from a couple of hundred meters.  Ponder on that a bit.  While this article doesn’t specifically address the .308/7.62×51, some of the principles are applicable.

Ammunition Revival

BY Herschel Smith
1 year, 3 months ago

Frank Miniter:

Two years ago I investigated ammunition shortages in the U.S. At the time many stores and gun ranges were rationing everything from .22 LR to 9mm to .223 Rem. ammunition. The shortage became so severe that rumors spread over Internet that the federal government was buying up ammo to purposely cause the shortages. There was so much paranoia that many ammo makers felt compelled to look into it and then publish explanations. Also, the National Rifle Association (NRA) investigated and the National Shooting Sports Foundation (NSSF), the trade association for gun, ammo, and related businesses, looked into the reasons for the shortages. They all came to the conclusion that consumer demand—fueled by record high gun sales—was behind the shortages.

Since then, this strong demand has been fueling a transformation of the ammunition industry—and much of this manufacturing growth is taking place in America.

Last week, for example, Advanced Munitions International (AMI) announced it will build a new ammo-making plant in Maryville, Tenn., that will employee about 600 people. This is a $553 million development project that is expected to be completed in late 2018.

Tennessee’s Governor Bill Haslam said, “This is an industry leader creating jobs that require a highly skilled workforce and it’s the kind of company that makes it obvious we’re moving toward a simple goal for Tennessee: becoming the number-one location in the Southeast for high-quality jobs.”

There is actually so much growth in the ammo industry right now that Jim Shepherd, editor and publisher of the Shooting Wire, wrote, “In the past few days, we’ve seen the announcement of a massive ammunition project in Tennessee, and the industry’s been titillated by Hornady’s ‘hint’ that they’re about to announce something really significant. And those are on top of the announcements that Browning is going to be offering a full ammo line, Ruger’s now offering a technologically advanced line of ammo in the common personal-defense calibers, and Sig Sauer’s now shipping their expanding lines of ammo.”

This might be the only time I ever do this, but I would like to thank Mr. Obama for aiding in the financial health of the gun and in this particular case, ammunition industry.  We couldn’t have done this without you.

Army And Marine Corps On M855 Ammunition

BY Herschel Smith
1 year, 11 months ago

Military.com:

But the Marine Corps and the Army’s decision to use two separate types of 5.56mm ammo is not a simple oversight.

The Army adopted the M855A1 in 2010 after years of struggling to find a lead-free replacement for the Cold-War era M855.

In recent years, troops also criticized the M855, saying it often delivered ineffective results on enemy behind battlefield barriers such as car windshields.

The M855A1 features a steel penetrator on top of a solid copper slug, making it is more dependable than the current M855, Army officials have maintained. It delivers consistent performance at all distances and performed better than the current-issue 7.62mm round against hardened steel targets in testing. It penetrated 3/8s-inch-thick steel at ranges approaching 400 meters, tripling the performance of the M855, Army officials said.

The Corps had planned to field the Army’s M855A1 until the program suffered a major setback in August 2009, when testing revealed that some of the bullets did not follow their trajectory or intended flight path.

The earlier design of the M855A1 featured a bismuth-tin slug which proved to be sensitive to heat, prompting Marine officials to stick with the M855 and also the Special Operations Science and Technology round developed by U.S. Special Operations Command instead.

Commonly known as SOST ammo, the bullet isn’t environmentally friendly, but it offered the Corps a more effective bullet, Marine officials have said.

I confess that until this article I didn’t know that the Army and Marine Corps were using two different types of ammunition.  If I’m not mistaken, the SOST is an open tip bullet with a lead core and copper shank.  It expands much like a hollow point should.

Saying that the better penetrating capability of the M855A1 through car windshields was the reason for transition from M855 to the M855A1 (with copper slug instead of lead) is like a recapitulation of the reasons for transitioning from the FMJ lead ball to the M855 in the first place.  It’s more likely that environmental concerns caused the Army to transition to the M855A1.  I cannot think of a worse excuse.

I will also remark that when I learned of the copper slug in place of the lead ball for M855A1 my thoughts immediately went to barrel wear and loss of rifling.  It appears that this is in fact a legitimate concern.

So in summary, the SOST is much like the .223 pointed soft point for game hunting, except that it has a copper shank.  If a reader would like to weigh in on the effects of the copper shank, please do so (in an educated fashion – and do not allow this to become yet another worthless argument over 7.62 v. 5.56).

Finally, don’t forget the main reason for the lethality of the 5.56 mm round, which is the fact that it is frangible and immediately fractures into pieces leaving multiple tracks through ballistics gelatin.  See the excellent paper Small Caliber Lethality: 5.56 mm Performance In Close Quarters Battle.  It appears that the Army has forgotten the simple things.

ATF Holds M855 Green Tip Ban In Abatement

BY Herschel Smith
1 year, 11 months ago

David Codrea:

The Bureau of Alcohol, Tobacco, Firearms and Explosives announced Tuesday it “will not at this time seek to issue a final framework” implementing a proposed ban on what it’s still insisting is “armor piercing ammunition.” The special advisory issued by the Public Affairs Division noted that with the comment period scheduled to close by next Monday, “ATF has already received more than 80,000 comments, which will be made publicly available as soon as practicable.”

‘Although ATF endeavored to create a proposal that reflected a good faith interpretation of the law and balanced the interests of law enforcement, industry, and sportsmen, the vast majority of the comments received to date are critical of the framework, and include issues that deserve further study,” the advisory explained. “ATF will process the comments received, further evaluate the issues raised therein, and provide additional open and transparent process (for example, through additional proposals and opportunities for comment) before proceeding with any framework.”

[ … ]

While arguments are correct that M855 ball ammo does not meet ATF’s own definition of “armor piercing,” the larger point, that there is no legitimate authority to impose such criteria in the first place, is being missed. So when ATF declares they’ll be back, until such time as that usurpation is addressed and resolved, it’s prudent to believe they will be, at the first political opportunity.

We could posit three theories behind what the ATF did today.  First, not even the federal regulators like to be called names such as traitors, douche, incompetent and bloated.  But that’s assuming they care about the American people, and the evidence for such an assertion is lamentable nonexistent.  So that theory suffers from being wishful thinking.

Second, the ATF understands that M855 green tip ammunition doesn’t meet the statutory definition of AP, or its corollary, that 5.56 mm lead ball ammunition can also penetrate soft body armor and is far more lethal in most circumstances.  Therefore, there will be a protracted legal battle waged against this regulation.

Third, the ATF realizes that a ban on M855 ammunition is meaningless without a ban on 5.56 mm ammunition, and that would have no more basis in law than a ban on any other type of ammunition.  Additionally, the ATF realizes they may be firing the first shot of a civil war were they to take an action like that.

Between theories 2 and 3, I don’t know which is more likely.  I dismiss out of hand the notion that the ATF feared action taken by the anemic, pathetic, pitiful Senate and House.  Readers may also have other theories (or combinations of the three proffered here).  But David is likely right on one thing.  The ATF will be back.

Josh Sugarmann On The M855 Green Tip Ban

BY Herschel Smith
1 year, 11 months ago

I know, about now you’re thinking “what can Josh Sugarmann teach me about M855 green tip ammunition?  Not much, except that it pays to understand just what the enemy thinks.  It’s also important to know just how behind the times they are in understanding what we think, but more on that in a moment.

This is despite the fact that ATF is only doing what the NRA and other members of the gun lobby consistently argue should be done: enforcing the gun laws already on the books. Opponents also allege that no law-enforcement officer has been shot with one of the cartridges fired from a handgun. Testing the veracity of that assertion is challenging, but the whole point of the ban on “armor-piercing” ammunition is to prevent law enforcement and first responders who rely on body armor from ever having to face assailants wielding handguns loaded with armor-piercing rounds.

Yet left unstated is the fact that ATF’s proposal, as detailed in a new report from my organization, the Violence Policy Center, is the direct result of the gun industry’s own actions.

Facing a continuing decline in household gun ownership, the gun industry is constantly engaged in efforts to create new product lines to sell to a shrinking consumer base. In recent years the industry has aggressively marketed AR-15 assault pistols that use common rifle ammunition, such as the 5.56-by-45-millimeter round used in AR-type assault rifles.

So it’s possible that Josh doesn’t really understand anything about rifle ammunition, or perhaps he does and is playing dumb (or lying) in order to deceive his idiot readers at Huffington Post.  But just to make sure you understand, let’s cover this for a moment.

Common 5.56 mm ammunition will penetrate soft body armor, all of it, period.  Kevlar will not stop 5.56 mm ammunition (lead ball) shot at 3200 FPS.  Nor will soft body armor stop most rifle rounds.  Soft body armor is [routinely] tested for 9mm pistol ammunition, not rifle ammunition.

ESAPI (enhanced SAPI plates, or the ceramic ballistic plates worn in ballistic plate carriers) are designed to stop rifle rounds, and are specifically tested for M855.  No cop today (or anyone else for that matter) wearing Kevlar is protected from any rifle round (unless it is from something like a pistol caliber rifle), and the existence of M855 or lack thereof doesn’t change that.  Likewise, a cop (or anyone else) wearing ESAPI plates is protected from rifle rounds, including the M855, and the existence of the M855 round or lack thereof doesn’t change that.  Finally, even ESAPI plates must stop a certain percentage of rounds (so there is some probability of fracture and penetration even with tested and specified rounds regardless of type).

So you understand, don’t you, that the M855 ban has absolutely nothing whatsoever to do with LEO safety, the liar in the White House notwithstanding?

As for the notion that gun owners are demanding that existing law be enforced, who is doing that?  No seriously, who is doing that?  Not me.  Are you?  If so, why?  Okay, perhaps the NRA has used that stupid argument, but we want open, constitutional carry in every state in America, and we want the Hughes amendment repealed, as well as prohibitions on things like SBRs in the NFA repealed.  That’s just a start.  We don’t want the existing laws to be enforced.  Every federal gun law is a violation of the constitution.  Every one.

Sugarmann then shows us a screen capture from the Rock River Arms web site.  Perhaps this will be good advertizing for them.  One can only hope.  Sugarmann ends with his usual propaganda that gun sales is down and ownership is increasingly focused on a smaller and smaller percentage of people.  Whatever.  If Josh wants to think this that’s alright with me.  The less they know about us and our beliefs, the better.

Read also Kurt Hofmann:

One (presumably very much unintended) argument against banning “armor piercing” handgun ammunition for private citizens came a while back from a very surprising source–the Violence Policy Center. As that group’s director, Josh Sugarmann, was cited in the U.S. News & World Report:

Gun control advocacy groups like Sugarmann’s say the body armor worn by the shooters in Newtown [which wasn’t “body armor,” anyway] and Aurora undermines the argument made by gun advocates that shootings can be stopped by someone with a handgun.

In other words, Sugarmann seems to be arguing that armed private citizens would have a reasonable chance at stopping mass shootings, if only they were not denied handgun ammunition capable of defeating body armor.

Yea, he is arguing first that guns are of no use against body armor so why would ordinary citizens have guns?; and second, there are millions of rounds in circulation that can defeat body armor, so they must be banned.  Sugarmann doesn’t care about consistency.  He’s just parroting the latest talking point.

Jerry Miculek On M855 Ammunition

BY Herschel Smith
1 year, 12 months ago

Jerry has give us a very informative video on M855 ammunition and it’s variants.


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