Improving Bullet Effectiveness

[Michael Courtney]

Effects of Barrel Friction on Muzzle Energy of Handgun Bullets

In a recent experimental study, we developed a method for measuring friction between the bullet and the barrel with a dynamic technique that determines the work done by friction as the bullet traverses the barrel. At relatively low velocities, this friction agrees well with measurements of the force of kinetic and static friction by standard methods.

Preliminary indications are that reducing friction can potentially increase the kinetic energy of handgun bullet by 25% in commonly carried service pistol cartridges such as 9mm, .40 S&W, and .45 ACP. This is important because our pressure wave studies have shown that the ballistic pressure wave represents an important contribution to rapid incapacitation by handgun bullets, and the magnitude of the ballistic pressure wave is proportional to the kinetic energy of the projectile.

Effects of Antimony Content on Jacketed Handgun Bullet Expansion and Fragmentation, and Resulting Magnitude and Location of the Ballistic Pressure Wave

Bullets that rapidly expand and fragment produce a ballistic pressure wave that is increased proportionally to the fraction of mass lost by fragmentation. Rapidly expanding and fragmenting bullets also produce volumes of crushed tissue that can be 2-4 times larger than bullets with moderate expansion and no fragmentation. Both of these factors can significantly decrease the average amount of time it takes for a handgun bullet to incapacitate a violent criminal or terrorist attacker.

Several factors influence the rate of expansion and fragmentation of jacketed handgun bullets. Effects of velocity, pre-cut and pre-stressed bullets, nose design, and jacket composition and design have been extensively studied. Most current bullet designs that expand rapidly and fragment do so in the first two inches of the wound channel, leading to sub-optimal location of fragmentation and pressure-wave effects, since most vital tissue is located deeper than 2 inches. It would be more effective to delay rapid expansion and fragmentation until deeper in the wound channel to optimally locate pressure wave effects nearer to vital tissues.

Preliminary research indicates that hardening the frontal section of a copper jacketed lead hollow-point bullet can delay the desired rapid expansion and fragmentation until the bullet has penetrated to a more optimum depth for creating more severe wounding and larger pressure wave that result from rapid expansion and fragmentation. The goal of this project is to quantify how hardening lead by the introduction of antimony can delay expansion to a more optimal depth.

Flattening the Pressure Curve to Increase Bullet Energy

An important limiting factor in handgun bullet effectiveness is the kinetic energy that can be delivered from a handgun-sized projectile launcher. The limiting factor for kinetic energy of handgun bullets is the pressure that can be contained in the chamber and barrel of the gun. Steel strength and bulk determine the maximum pressure that a chamber and barrel can contain. However, the kinetic energy of the bullet depends on the average pressure as the expanding gasses propel the bullet down the barrel. Therefore, flattening the pressure curve, by raising the average pressure closer to the peak pressure, is a viable approach to increasing handgun bullet effectiveness.

The chemistry of smokeless gun powders has changed very little over the last 100 years with burn rates controlled by changing the size and shape of the nitrocellulose propellants, the addition of burn rate retardants, and also by the use of some double-base propellants that include nitroglycerine. Combined with reducing barrel friction, achieving significantly flatter pressure curves can potentially double the kinetic energy of handgun bullets without increasing the strength, cost, or bulk of the handguns themselves.

Reducing barrel friction is an important first step, not just because friction robs kinetic energy, but also because friction in current bullet/barrel designs is unpredictable, and when it is unexpectedly high, it leads to a pressure-induced increase in burn rate with current propellants. This can lead to pressure spiking which increases the peak to average ratio of the pressure curve.

Beyond reducing barrel friction, several chemical approaches are possible to flattening the pressure curve. These include using propellants that are less progressive in their burn characteristics, including endothermic components in the propellant so that the propellant itself can absorb energy above a certain pressure or temperature threshold, and including propellants with many degrees of freedom so that the early expansion of the unburned propellant exerts greater cooling on the burning propellant and flattens the pressure curve.

The combination of reducing barrel friction and keeping the barrel pressure closer to the maximum can increase bullet energy by at least 100% without increasing the size or bulk of service caliber handguns.

Michael Courtney

 

[MCgunner]

While I find this quite interesting to read, I can't wait for all the Faklerite/Taylorist momentum gurus to chime in....

When it comes to volume of BS, I think few subjects are as inspirational as terminal ballistics. Its the big bullet agenda that does it and it seems to me the adoption of the Beretta M9 in the mid 80s amplified it. While this post deals with increasing kinetic energy, those two words are curse works for the faklerites. They couldn't care less so long as the bullet is BIG. Why would velocity matter?

BTW, interesting. I've read that barrels from Ruger have less bullet friction than other manufacturers, but I've never been able to discern the differences in chronograph testing between guns of different makes, otherwise similar. So, that might be BS. Also, I'm wondering if one can really control expansion that closely? I mean, I want the danged bullet to open up. Seems a bit presumptuous of me to want to control the expansion in that much detail. I've always went for a BIG hollow point, but I know that's not very scientific.

The powder burn thing is an obvious one. But, one also has to reckon on barrel length. The magnums burn slower powders. They hold pressure further down a barrel than a faster powder, say 2400 vs bullseye. But, all that pressure is lost in a short tube. That's sorta the problem with .357 snubbies and why companies are coming out with "snubby loads" as I understand it.

 

[Majic]

Why harden the lead core when it's simplier to redesign the copper jacket? Remember that the lead core has to be swaged into the jacket and hardening the lead will make the swaging process harder which will stress the jacket.
Shortening the time for peak pressure wave will benefit a shorter barreled handgun, but will degrade the effectiveness of the longer barrel. Why go thru the trouble of re-engineering a slower powder to behave like the faster powders already on the market. Fragmentation of bullets is what the bullet makers have been striving to defeat. They want a bullet to expand to it's largest diameter while retaining all of it's mass for the weight needed for penetration. Bullet to bore friction can be easily reduced by eliminating the jacket. The jacket being a harder metal raises this friction, but if you reduce it to much then the bullet could slip in the bore degrading the rotational spin thus affecting the external ballistics. Bullets must perform over a wide variety of velocites so they have to be flexible not specific unless you want to drive the price of the bullet way up with the many different bullets needed for all the velocites it may be shot at.
Nice analysis, but it sounds as if you are trying to re-invent the wheel.

 

[otomik]

on reducing barrel friction, polygonal rifling is becoming more common, I also like the concept of progressive rifling. both of these conserve energy without getting into the mysterious area of moly coating and whatnot.

 

[taliv]

or heck, moly coating

 

[Michael Courtney]

Why would velocity matter?

Velocity doesn't matter as long as the velocity is in a range for the given bullet to expand reliably and penetrate to the desired depth. Aside from this consideration, incapacitation depends on energy, penetration depth, expanded diameter, and retained mass.

BTW, interesting. I've read that barrels from Ruger have less bullet friction than other manufacturers, but I've never been able to discern the differences in chronograph testing between guns of different makes, otherwise similar.

If all you do is reduce barrel friction with the same loads, you won't see more velocity, because the lower friction meaks that the pressure pushing the bullet never gets as large.

Increasing bullet energy requires both reducing barrel friction AND adjusting the powder to keep the pressure near the maximum for the cartridge.

It is well known that if you coat bullets in molydemum disulfide, the reduction in friction causes either no change or a slight grop in velocity for the same powder charge. However, if you develop a load to achieve the same pressure, one usually sees more velocity with lubricated bullets.

Moly has been used extensively in rifle bullets. However, moly only reduces the frictional losses by a small amount. This might be the best one can do at the velocities and accuracy level expected from centerfire rifles. In contrast, one can reduce the friction by 80% or more with other methods that have been shown to work well at velocities up to 2200 FPS and maintain accuracy levels of 3-4" at 100 yards.

Using these methods and adjusting the powder charge to maintain the pressure near the cartridge rating can increase the kinetic energy of the common service calibers (9mm, .40 S&W, .45 ACP, .357 Sig) by 100 ft-lbs.

So, that might be BS. Also, I'm wondering if one can really control expansion that closely? I mean, I want the danged bullet to open up. Seems a bit presumptuous of me to want to control the expansion in that much detail. I've always went for a BIG hollow point, but I know that's not very scientific.

You are right that delaying the initiation of expansion until 4-6" of penetration, yet ensuring reliable expansion once that depth is reached presents a significant technical challenge.

I'm not saying it's an easy task, but I believe it is achievable and worth condsidering. Keeping the cost to under $1 a bullet is actually more challenging than obtaining the desired performance.

The powder burn thing is an obvious one. But, one also has to reckon on barrel length. The magnums burn slower powders. They hold pressure further down a barrel than a faster powder, say 2400 vs bullseye. But, all that pressure is lost in a short tube. That's sorta the problem with .357 snubbies and why companies are coming out with "snubby loads" as I understand it.

This is definitely a technique that depends on a relatively close match of the load and the gun. Advanced propellent techniques that show significant improvements in 4-5" barrels may well perform horribly in shorter barrels. But expecting loads to perform well in the full range of barrel lengths does rob performance from what is achievable in a full-sized service caliber handgun. And this gap will most likely widen with improved propellant technologies.

Michael Courtney

 

[Michael Courtney]

Why harden the lead core when it's simplier to redesign the copper jacket?

Copper jacket designs have proven a good choice for controlling expansion once it is initiated. The goal of hardening the lead is to delay the initiation of expansion. And the approach might not need to harden the entire lead core, only the frontal section. Think of something like a Nolser Partition with a hardened lead core up front and the normal lead in the back.

Fragmentation of bullets is what the bullet makers have been striving to defeat. They want a bullet to expand to it's largest diameter while retaining all of it's mass for the weight needed for penetration.

If 12" of penetration can be assured, fragmentation actually makes important contributions to wounding and rapid incapacitation. This can be accomplished in a Nosler Partition type of design where the front half of the bullet fragments and the back half holds together and penetrates.

Most of the Partition rifle bullets only retain 60% or so of their mass because they lose most of the frontal section to fragmentation. The Partition handgun bullets retain more of their mass. A handgun bullet design that delayed expansion until a penetration depth to 4-6", then expanded and lost 40% of its mass in the next 2-3", and then penetrated 12" deep or so with the remaining core, would represent a significant improvement in bullet performance over the designs available today.

Bullet to bore friction can be easily reduced by eliminating the jacket. The jacket being a harder metal raises this friction, but if you reduce it to much then the bullet could slip in the bore degrading the rotational spin thus affecting the external ballistics.

In muzzleloaders, sabots are used which have very little friction and have no trouble at all imparting rotational spin to the bullet. (I'm not saying sabots represent a workable approach for handguns, just that reducing barrel friction doesn't always mean failure to impart spin).

However, since the jacket is now an important aspect of terminal performance, I doubt that eliminating the jacket would be a workable approach. Probably what needs to be done is to give the existing jacket (retained for terminal performance), another jacket of a material which minimizes barrel friction. Federal had a nylon coated bullet, and a teflon coating has also been used. Of course the goal is to reduce friction without creating a political firestorm.

Michael Courtney

 

[Michael Courtney]

on reducing barrel friction, polygonal rifling is becoming more common, I also like the concept of progressive rifling. both of these conserve energy without getting into the mysterious area of moly coating and whatnot.

Reducing friction with an improved barrel will not give the full benefit, because loads need to be designed not to exceed a pressure limit in any available barrel.

Reducing barrel friction with a different barrel can give a small increase in bullet energy, but a bigger increase is possible if the powder charge is tweaked to keep the pressure near the maximum allowed for the cartridge. This is only possible if friction is reduced changing the bullet. (Or by creating a new cartridge where every barrel in existance allows for loads that have powder charges optimized for the reduced barrel friction.)

I don't think that moly or any of the other centerfire rifle coatings is the proper approach here. Probably a material something more like a muzzleloading sabot that forms an outer layer on the bullet. It doesn't need to be nearly as thick as muzzleloading sabots, nor does it need to come off to reduce barrel friction.

Michael Courtney

 

[Double Naught Spy]

This is important because our pressure wave studies have shown that the ballistic pressure wave represents an important contribution to rapid incapacitation by handgun bullets, and the magnitude of the ballistic pressure wave is proportional to the kinetic energy of the projectile.

Are you referring to hydrostatic shock?

Velocity doesn't matter as long as the velocity is in a range for the given bullet to expand reliably and penetrate to the desired depth. Aside from this consideration, incapacitation depends on energy, penetration depth, expanded diameter, and retained mass.

The bold is my emphasis. All that science and yet the most basic fundamentals are forgotten. Energy, penetration depth, expanded diameter, and retained mass don't mean squat if you don't have vital structures or organs affected.

 

[grendelbane]

More velocity might be nice. And maybe you can achieve higher velocity with a different barrel material, or a different barrel construction. Or a change in the bullets material or construction.

Newer design powders might also enable higher velocities.

The problem, as I see it, is that current technology can already launch handgun bullets at higher velocities than I want to shoot. I know from past experience that I can handle a handgun firing an 158 grain bullet at 1300 FPS, but if the weight of the bullet is increased to 230 grains the velocity has to decline by over 400 FPS for me to be able to handle the recoil.

The need to ensure sufficient penetration of an expanding bullet is going to dictate the sectional density of the bullet and therefore its weight.

So unless you are considering much smaller caliber bullets at much higher velocities I do not see what you are trying to accomplish.

 

[grendelbane]

A solid copper SWC does not meet my definition of an expanding bullet.

Likewise, 10" does not meet my definition of adequate penetration.

A 60 grain bullet at 2300 FPS would be controllable.

I have loaded zinc bullets to outrageous velocities also, but of course, zinc does not expand.

 

[jeepmor]

Friction versus powder load---polishing the bore.

Michael,

You continually tie friction and powder charge together in this thread but admit that the friction really is not the key, it's the powder charge being set to near max. Please elaborate. You've covered that reducing friction too much will create instability due to the bullet not grabbing the rifling enough, losing some of it's spin energy, making the bullet unstable.

But I don't see how reducing the friction is making a difference, you keep saying it's the powder charge. So are you suggesting we polish our pistol bores?

I ran a fine rubbing compound through my barrel with a double patch and a tight fitting jag. With the break in bullets running from 400-1200 grit, I think think a fine or medium cut rubbing compound is a good conservative tradeoff since the cut is about 1200-2000 grit, in my guestimation. I choose to spend more time lapping by hand slowly.

It worked very well in that it removed a lot of black gunk out of the barrel that started clean as a whistle, it became noticeably smoother to the eye and now has a polished look to it. I don't have a chronometer to compare velocities, but it is now a breeze to clean and I do not get the copper buildup in my typical 100-200 round shooting session. I can now clean the weapon in a few minutes compared to nearly an hour of scrubbing before. off topic a bit, but I do beleive there is a big benefit to lower friction even if it's not played out in ballistic performance at the bullet. It has increased my satisfaction with this hobby by merely allowing me to spend more time shooting and less time cleaning.

jeepmor

 

[MCgunner]

Quote:
Originally Posted by MCgunner
Why would velocity matter?



Velocity doesn't matter as long as the velocity is in a range for the given bullet to expand reliably and penetrate to the desired depth. Aside from this consideration, incapacitation depends on energy, penetration depth, expanded diameter, and retained mass.

Oh, yes, I agree with most of what you wrote. Velocity is most important in energy as it is squared. However, as I see some have posted, the big bullet types, the real proponents, say energy isn't what matters, but momentum. They say that because velocity is linear in relation to momentum, squared in relation to energy, but they're most definitely full of it. Momentum knocks bowling pins off tables, but energy destroys tissue. And, yeah, I'm sure you're talking about center mass hits here.

 

[Majic]

In muzzleloaders, sabots are used which have very little friction and have no trouble at all imparting rotational spin to the bullet.

You think they impart very little friction? Try loading a few. You will find they load no easier than the lubed pure lead bullet or the patched roundball. Sabots are used to make use of the plentiful handgun bullets and the fact that so many shooters today think a jacketed bullet is needed for everything. The shot velocity is raised because you now are moving a mass of less weight as the handgun bullets used are smaller in diameter and lower in weight than the lead muzzle loading bullets that fit the bore.

 

[Michael Courtney]

You continually tie friction and powder charge together in this thread but admit that the friction really is not the key, it's the powder charge being set to near max.

Both minimal friction and maximum pressure are important. Keeping the internal barrel pressure near the maximum creates kinetic energy. But friction can rob over 100 ft-lbs.

But I don't see how reducing the friction is making a difference, you keep saying it's the powder charge. So are you suggesting we polish our pistol bores?

The solution isn't in the barrel, unless you load specifically for an individual barrel (or a group of barrels that share the same improvements). If you load to max pressure in a low-friction barrel, you will blow up a gun with normal barrel friction.

Consequently, if one is going to load for an existing cartridge, it makes more sense to concentrate on the bullet when reducing barrel friction.

Keeping barrel friction below a certain threshold (say the bullet can move in the barrel with < 40 lbs of force) would allow more advanced powders to optimally improve performance, because most of the resistance to bullet movement is then intertial.

But keep in mind that I'm talking about a level of friction where you can push the bullet through the barrel by hand. I am not talking about slight improvements in friction that would come from a lubricant or from polishing.

Michael Courtney

 

[Michael Courtney]

You think they impart very little friction? Try loading a few.

We have, with the stock resting on a force plate to measure the required force. The force was between 35 and 40 lbs all the way down the barrel. We also used an advanced technique to measure the frictional force coming out of the barrel at various velocities in the 700-1200 FPS range. The frictional force while the bullet was exiting the barrel was also in the 35-40 lb range.

The same amount of frictional force in a 4" pistol barrel would only result in losing 14 ft-lbs or so to barrel friction. Compare that to the typical loss of well over 100 ft-lbs of energy with common bullet designs. Have you ever tried to push a stuck bullet down the barrel? With normal JHP bullets, it takes 300-500 lbs. The amount of lost energy is simply the force required to move the bullet times the length of the barrel in feet.

Michael Courtney

 

[Michael Courtney]

And we've long had the ability to achieve such velocities. The issue is how to do this, with a bullet that also penetrates and expands. A solid copper hollowpoint provides such performance, in 9x23 Win, 9x25 Dillon, 10mm, 38 Casull, even .45 Super. The bullet wts run between 60 and 80 grs, with velocities of over 2200 fps in 4"-5" barrels. It's simply a question of do you care enough about real combat perfomance to pay $3 a shot. Many,many people pay such a price for Glasers, MagSafes, and such, so the issue is getting the Solid Copper bullets into mass production, using automatic screw machine technology.

Velocity isn't the key issue. You need three things for the largest possible pressure wave (sometimes mistakenly called hydrostatic shock):

1. Maximum Kinetic Energy (1000 ft-lbs would be nice)

2. Controlled penetration. Most law enforcement applications call for 12", 10" might be better for some CHL applications and risk assessments. But you want to meet the minimum penetration for the application, without too much.

3. Controlled fragmentation that does not sacrifice penetration. A 40% loss of mass can increase the pressure wave magnitude by 40%.

Velocities above 2000 FPS, while technically interesting are probably not commercially viable outside of law enforcement and military applications. What ammo company wants to put the money and effort to bring a 2200 FPS handgun load to market only to have it outlawed as "cop killer" at the time of general release?

If we set 2000 FPS as a practical upper velocity limit for commercial viability (to steer clear of vest penetration problems), we need a 115 grain bullet to get 1000 ft-lbs of energy. This would put recoil in the same league with the hottest .45 ACP loads currently available (230 grains at 1000 FPS): stout, but manageable with adaquate training and perhaps a compensator.

The 9x25 Double Tap loading pushes a 115 grain Gold Dot to 1800 FPS, which is an impressive 827 ft-lbs of energy, but it is clear some technological improvements are needed to the internal ballistics reach 1000 ft-lbs.

We've played around a bit with hollow base bullets. There is some reduction of friction, but much less friction is possible either:
1. In a sabot
2. With a bullet coated with a sabot-like material
3. Using an slightly undersize bullet with a plastic skirt (like PowerBelt muzzleloading bullets.

In addition to improving internal ballistics (reducing friction, improving propellants) to reach 2000 FPS with a 115 grain bullet, one also needs to solve the bullet performance problem. Copper bullets show a lot of promise for penetration, but the are not as promising with respect to fragmentation as a partition-type of design with a soft lead frontal section that will expand and quickly erode a way leaving a base section retaining 60% of the mass to ensure penetration.

This would provide .223 levels of terminal performance in a commercially viable handgun load.

Michael Courtney

 

[grendelbane]

A 10mm case filled with a compressed load of Unobtainium powder, and a 9mm wonder bullet in a sabot might make your 2000 FPS mark. Especially if you use a tapered bore.

It is going to be loud, and it will probably kick more than I want. (A man has to know his limitations). A good comp would help with the recoil, but makes it even louder.

It would be pretty close to what the M1 carbine produces, ballistically. It definitely needs a well designed bullet to out perform contemporary technology.

To keep it from being loaded with conventional 10mm cartridges, which might not function too well in the squeeze bore, it might be best to make it a .41 caliber. Now we need new brass, something akin to a lengthened and strenthened .41 AE.

Accuracy will probably not be anything to write home about.

There is a revolver wildcat I have seen that uses a .41 magnum case necked down to .357. This would produce the ballistics that you want with conventional powders. If you go that route, all you need are the wonder bullets.