Cartridge with the highest velocity

[CV32]

Okay let's try this... What is the fastest cartridge today in a hunting rifle let's say 22-26 inch barrel that is commercially made?

It was the .204 Ruger. Not sure if it has since been exceeded, and I suppose it also depends on the definition of "commercially made".

 

[JJ-65]

Okay let's try this... What is the fastest cartridge today in a hunting rifle let's say 22-26 inch barrel that is commercially made?

My .257 Weatherby shooting 80gr ttsx bullets at 4000 fps.

 

[SandRoad]

The limit is related to the speed of sound in the gun gas (the products of the powder's combustion), not the speed at which the powder burns. The outright theoretical limit is what's known as a "free expansion", that's the case where you have a bullet with a weight of zero, and your gun gas expands at a very high (but finite) speed.

Your explanation is great. When I said flame front, it was obviously not quite right terminology but concept was correct. "Flame front" was meant to include "products of combustion", and velocity of expansion, not the burning speed of powder, and I have seen (somewhere) it being refereed to as this.

Interesting stuff you wrote over that at post #30. I had never heard of "firebrakes" in an artillery charge before, though it sounds like a plausible concept (this would be an effort to achieve the "travelling charge effect"). And it's always nice to read about HARP stuff.

I don't know what "firebrakes" are really called, but it does create the travelling charge effect. I remember reference to them being used in large bag loaded artillery/navy guns. Bull used wooden "spacers" in his HARP guns to achieve the travelling charge effect.


I can't imagine what Gerald Bull would have been able to accomplish with today's real time pressure instrumentation and powders. He was using surplus WW II powder for his HARP experiments.

 

[rnbra-shooter]

I don't know what "firebrakes" are really called, but it does create the travelling charge effect. I remember reference to them being used in large bag loaded artillery/navy guns. And I believe Bull also used this in his HARP guns.

(quickly getting off topic but why stop now....? ;-) I've never heard of Bull using this in his HARP guns (though to be honest I paid most of my attention to the 16" one), I think he was having ignition uniformity problems with the large charges he was using and hence the multipoint ignition system that he went to in order to achieve reliable simultaneous ignition of the whole charge. I would think that getting correctly staged ignition would be pretty challenging(!), and probably something to be dispensed with in order to avoid the potential risk of delaying the project with a journey down an unnecessary R&D rathole.

They sure did lots of interesting things. I was recently rereading on HARP and this time noticed that they evacuated the air in the barrel between the bullet and the muzzle, this gained them a hundred fps or so.

It would be interesting to find out what performance level he was targeting with his Iraqi supergun, and what his design approach was going to be. I'm curious if he ever decided to try the V-3 route or not.

 

[Suputin]

i remember a cartridge .17/.50bmg a .17 cal bullet with a necked down case of a .50bmg. reports of a there abouts 10,000 fps, and i think u get about a couple of hundred shots before there is some definate change in accuracy as the barrel is being destroyed inside out.

Not physically possible. As others have posted there is a limit to how fast a powder based system can push a projectile. This limit is not based on pressure but on how fast the propellant gas can expand which is also based on how fast the powder burns. The practical limit to a powder based system is ca 5000 - 5500 fps.

I am actually amazed by those published numbers for the 22-243 Middlestead. I was unaware that it was possible to exceed 5000 fps. Those 5300 fps velocities are crazy. It would be interesting to see one of those 30gr bullets vapourize a gopher. However I am certain that barrel life would be greatly reduced with those kinds of velocities.

I can't imagine what Gerald Bull would have been able to accomplish with today's real time pressure instrumentation and powders. He was using surplus WW II powder for his HARP experiments.

I recently met a guy who has access to Bull's work and he is one of the most interesting people to talk to that I have ever met.

 

[jayz]

I was just flipping through the hornady handbook 7 ed and found 4 that break the 4000+ fps.

204 with a 32gr 4200fps
22-250 with a 40 gr 4100fps
220 swift with a 40 gr 4300fps
223 wssm with 40 gr 4600fps

These are max safe loads but with a little experimentation the wssm might go 5000. I have a swift and the only problem is that the faster you go the more centrifugal force there is. The thin jacket bullets don't stand up to it.

 

[SandRoad]

223 wssm with 40 gr 4600fps

These are max safe loads but with a little experimentation the wssm might go 5000. I have a swift and the only problem is that the faster you go the more centrifugal force there is. The thin jacket bullets don't stand up to it.

What load would that have been? The Hodgdon online manual only goes up to 4415 fps, with a 36gr bullet.

"Some experimentation" might get a hundred fps or less, nowhere near 5,000 fps.

One concept about peak pressure is that it is only loosely related to velocity. The pressure peak might only last for part of a of millisecond, of a bullets several millisecond travel down the barrel.

The peak in a magnum rifle typically pressure occurs after the bullet has travelled a couple inches, and only lasts for a fraction of an inch. From that point to the muzzle the chamber pressure gets lower.

 

[jayz]

The load is a 40gr V Max with 45.2gr of IMR 4064. The book says that it's the max load.

I just looked at the IMR website and it said that the max was 4400+.

My book is from 2007 so it might be dangerous.

It would be nice to here from someone that owns one.

 

[tootall]

Just thinking out loud here, DEFINITELY NOT recommending a load, but would mixing two powders of different burn rates help to flatten out the pressure curve?
Having a pressure curve that is less peaky, and more flatter would theoretically give more boost, wouldnt it?

Probably the more effective way to pump up the velocity would be to use a plastic sabot along with a squeeze bore barrel like the Gerlich guns
http://en.wikipedia.org/wiki/7.5_cm_Pak_41

 

[Meph]

Just thinking out loud here, DEFINITELY NOT recommending a load, but would mixing two powders of different burn rates help to flatten out the pressure curve?
Having a pressure curve that is less peaky, and more flatter would theoretically give more boost, wouldnt it?

Probably the more effective way to pump up the velocity would be to use a plastic sabot along with a squeeze bore barrel like the Gerlich guns
http://en.wikipedia.org/wiki/7.5_cm_Pak_41

Your first idea is quite interesting. I've been thinking of that too, a fast burning powder mixed with a slow burning powder might be able to generate a standard chamber pressure over a longer period of time - seems to me like most of the rest of the barrel would need to be as strong as the chamber so the long pressure impulse doesn't rip through the barrel as it's still going boom past the chamber.

I'd expect pretty fast erosion as the heat blast would be much longer and would heat up the barrel a lot more.

Second idea is also pretty cool, and deals with sabots that I do like. Sabots are a nice way of sending something fast without necking down. 30-06 sabots for .22 bullets show how fast you can throw a bullet while retaining barrel life. Cool in my book.

 

[BattleRife]

.".

 

[rnbra-shooter]

Flattening out the pressure curve would be a very good way to increase velocity. Specifically, reducing the rate at which pressure falls after the pressure peak is reached (which is after 1.5-2" of bullet travel).

The challenge is that you need to match the gas generation rate of the powder, with the accelerating motion of the bullet. So you need approaches that either delays some of the burning during the pre-peak period, or at least slows it down, and then accelerates the burn rate after the pressure peak has been reached (more realistically, fights against the decline in burn rate that happens once the pressure begins to fall).

Using two different powders with different burn rates means you're obviously thinking along these lines. Instead of making your powder charge "more progressive" (i.e. reserving some of the burn for later in the cycle), what typically happens is that you end up with an overall burn profile that is basically averaged between the two sub-charges. This is because you have no way of preventing the quick-burning powder from starting to burn at the beginning of the ignition cycle, so it is also contributing to the pressure curve rise (where you really aren't looking for help). If you could find a way to delay ignition of the faster powder until the pressure peak had been reached, that would be a good contribution in the direction that you are looking,

If you are interested in 5000+ fps speeds, another factor starts to come into play and that is that mass of the gun gas itself starts to become relevant. At these speeds and higher, the energy needed to get the gun gas itself moving at high speeds becomes a greater and greater fraction of the overall energy available (and therefore a diminishing fraction is available to go into the bullet's speed). This is why "light gas guns" are used for super high velocities.

Ain't interior ballistics fun...? ;-)

 

[SandRoad]

Light Gas Gun - Interesting, just not very portable....... A big airgun, just like a "magnum" springer....

http://en.wikipedia.org/wiki/Light_gas_gun

A light gas gun works on the same principle as a spring piston airgun. A large diameter piston is used to force a gaseous working fluid through a smaller diameter barrel containing the projectile to be accelerated. This reduction in diameter acts like a lever, increasing the speed while decreasing the force. In an airgun, the large piston is powered by a spring or compressed air, and the working fluid is atmospheric air. In a light gas gun, the piston is powered by a chemical reaction (usually gunpowder), and the working fluid is a lighter gas, such as helium or hydrogen (though helium is much safer to work with, hydrogen offers the best performance [as explained below], and causes a lesser amount of launch tube erosion). One addition that a light gas gun adds to the airgun is a rupture disk, which is a carefully calibrated disk (usually metal) designed to act as a valve. When the pressure builds up to the desired level behind the disk, the disk tears open, allowing the high-pressure light gas to pass into the barrel. This ensures that the maximum amount of energy is available when the projectile begins moving.

One particular light gas gun used by NASA uses a modified 40 mm cannon for power. The cannon uses gunpowder to propel a plastic (usually HDPE) piston down the cannon barrel, which is filled with high-pressure hydrogen gas. At the end of the cannon barrel is a conical section, leading down to the 5 mm barrel that fires the projectile. In this conical section is a stainless steel disk approximately 2 mm thick, with an "x" pattern scored into the surface in the middle. When the hydrogen develops sufficient pressure to burst the scored section of the disk, the hydrogen flows through the hole and accelerates the projectile to a velocity of 6 km/s (22,000 km/h) (about 20,000 fps) in a distance of about a meter.

NASA also operates light gas guns with launch tube sizes ranging from 0.170 inches (4.3 mm) to 1.5 in (38 mm) at Ames Research Center. These guns have been used in support of various missions beginning with Apollo reentry studies in the 1960s and most recently for high-speed thermal imaging. Velocities ranging from 1 km/s up to 7 km/s can be achieved. The largest of these involves a 6.25-inch (159 mm) diameter piston weighing more than 46 pounds (21 kg) to compress the hydrogen.
Two light gas guns at Arnold Air Force Base's Hyper-velocity Ballistics Ranges.

Arnold Air Force Base's Range-G is the largest light gas gun facility in the United States[1]. Range-G utilizes interchangeable launch tubes ranging from a bore diameter of 3.3 inches (84 mm) to 8.0 inches (200 mm) with a 14.0-inch (360 mm) piston weighing up to 2,300 pounds (1,000 kg). Projectile velocities can reach up to 4.5 kilometres per second (16,000 km/h) for the 8.0-inch (200 mm) configuration and up to 7 kilometres per second (25,000 km/h) for the 3.3-inch (84 mm) launcher configuration[1]. The primary use of the range facilities at Arnold Air Force Base is the measurement of released kinetic energy upon projectile impact.

 

[rnbra-shooter]

(wikipedia's description of a light gas gun).... hmmm, the part you quoted misses the main point, and in fact does a fair bit of misdirection. That article could use a *lot* of cleanup (not by me though). The area reduction is not at all an essential feature of a light gas gun and to compare it to a "lever" is misleading as to the important features of a light gas gun; the use of a light gas (e.g. hydrogen or helium) is a key feature, the reason being the higher speed of sound in lighter gases.

 

[thebigslide]

Using two different powders with different burn rates means you're obviously thinking along these lines. Instead of making your powder charge "more progressive" (i.e. reserving some of the burn for later in the cycle), what typically happens is that you end up with an overall burn profile that is basically averaged between the two sub-charges. This is because you have no way of preventing the quick-burning powder from starting to burn at the beginning of the ignition cycle, so it is also contributing to the pressure curve rise (where you really aren't looking for help). If you could find a way to delay ignition of the faster powder until the pressure peak had been reached, that would be a good contribution in the direction that you are looking,

Ain't interior ballistics fun...? ;-)

Well, here's the thing about "powder burn rate." It isn't really a measure of one thing. Powders have an ignition energy and a combustion rate constant. Slow powders typically have a high ignition energy and a low combustion constant - and vice versa, but a powder that is slower than another may have a lower ignition energy. A good rule of thumb is that temperature sensitive powders have relatively low ignition energies.

Most powders produce relatively the same gas mass per propellent weight, one exception being certain shot shell powders and fast pistol powders that produce less volume due to the high ratio of nitroglycerine content. Another exception would be very slow machine gun powders that contain very high amounts (relatively) of free carbon, designed to cool the flame and slow the consumption rate.

The ignition energy of any powder is so low that, in a typically designed cartridge, by the time the first few percent of a powder charge has been fully consumed, the full charge has been ignited. Compressed loads in long narrow cartridges would provide an exception. At this point, the bullet has barely moved down the barrel and in some cases hasn't even cleared the throat. The peak pressure normally occurs shortly after the full charge has been ignited. This is due in large part to the rate of combustion of propellent being tied to chamber pressure and temperature. The combustion rate constant is a scalar factor in the rate of combustion. Temperature and pressure are also multiplicitive factors in the combustion rate.

The rate of ignition of propellent is also tied to enthalpy within the chamber, which, in layman's terms is a product of pressure and temperature. So, as the propellent burns, it also provides the energy which ignites further powder _more_rapidly. This is part of the diminishing returns on case capacity. As you add more powder, any additional charge is ignited much more rapidly than the initial charge ignited closer to the case head. And so, cartridges with a large case capacity must use a 'slower' powder with a higher ignition energy and slower consumption rate to compensate.

If you mix a fast burning powder with a slow burning powder, what you end up with is a charge where the fast burning powder will promote quicker ignition of the slow burning powder - IE, the maximum chamber pressure will come on sooner. This is the idea behind multiplex muzzleloader charges. The fast burning BP ignites a small amount of high-gas volume smokeless and, as a result, the same gas volume is produced at a lower powder charge and will less resultant fouling. Effectively, by the fast burning powder providing more activation energy, you are doing the same thing as LOWERING the ignition energy of the slower burning secondary charge. If the secondary charge is already approaching critical pressure before the addition of a fast burning primary ignition source, this is a BAD THING (tm).

One idea I've been playing around with is the idea of using a compressed charge pellet - similar to the pellets that were used in experimenting with caseless ammunition. These pellets are porous rather than a large homogenous grain and so, burn much faster than a single large grain would. A fast, low gas mass propellent could be used to evenly ignite the slow burning pellet as well as provide additional gas volume by bumping the bullet down the bore. This is how pyrotechnic shells are designed.

In pyrotechnics, we regularly layer various propellents in a shell to produce various effects, such as color change, burn rate, and fragmentation in arial shells. A similar pelletized charge could be easily enough produced for a cartridge rifle, but the caveat is that they need to get into the cartridge behind a bottleneck. I had an idea that one could make a compressed propellent "stick" to be loaded down the bottleneck as a secondary charge and then an additional granulated primary charge could be added around the primary charge. I tried modelling these and realized it wouldn't work because the secondary charge would lead to inconsistent ignition of the primary.

What I came up with is the idea of using a stick-type primary charge. A very very fast shotgun powder is compressed and extruded as a single tube. This tube is then surrounded by an extruded grain type very slow secondary charge with a very high activation energy (like a modified machine gun powder). The flame front from the primer will ignite the primary charge very quickly from the head to the shoulder and also provide additional accelleration for the projectile, reduce the internal chamber volume and pressure. The secondary charge is ignited by the primary charge, but due to the decreasing volume and delayed ignition, reaches peak accelleration much later in the game. The gotcha is designing the compressed primary charge such that it sits consistently in the case throughout the combustion. A stick form is ideal for this since it could be designed to anchor in the primer pocket.

It is also ideal to create a primary charge that burns very fast near the head and slower near the throat to provide additional activation energy to the TOP of the secondary charge. These charges could be produced in a press as a cone narrow shape with additional carbon added near the base to slow the burn rate there as well as shroud the primary charge near the base.

For obvious reasons, the barrel would need to be designed very strong for quite a distance up the barrel. Alas, I don't have the technology to test this safely, so I have not.

I'm also not sure what the legalities are of testing something like this, but, in a home made canon where "anything goes", would be fun to try.

 

[thebigslide]

I'll add the safety note here so it's easier to see:

If you add a fast burning powder to a slow burning powder, they ignite as one - not one after the other - no matter how carefully you fill the case. You end up with faster burning characteristics than the slow burning powder. This is a possible KABOOM unless you really know what you're doing.

In the case of a slow machine gun powder with a fast burning powder added, you also end up with high gas volume and significantly higher pressures than if you just used the machine gun powder - KABOOM!

 

[Meph]

I'll add the safety note here so it's easier to see:

If you add a fast burning powder to a slow burning powder, they ignite as one - not one after the other - no matter how carefully you fill the case. You end up with faster burning characteristics than the slow burning powder. This is a possible KABOOM unless you really know what you're doing.

In the case of a slow machine gun powder with a fast burning powder added, you also end up with high gas volume and significantly higher pressures than if you just used the machine gun powder - KABOOM!

Your two posts were awe inspiring. I'm reading them over a few times, fascinating!

One thing though, what about separating the two powders with a barrier that burns away? For example, a pouch or even a "wall" between the two charges made of a dacron-fluff like material that contains a powder, separating it from the other.

 

[rnbra-shooter]

For what it's worth the ignition energy needed to ignite a powder is only indirectly related to its burn rate properties (it's true that slower powders often have higher ignition energy requirements, but that's because they've used heavier deterrent coatings in order to give them a slow burn profile, not fundamentally because they are slower powders).

Four main factors control powder burn rate:
- size of the powder kernel
- shape of the powder kernel (and as a result of this, how the surface area of the powder kernel changes as a function of the amount of the powder kernel that has burnt)
- surface deterrent coatings, if any
- deterrents diffused into the powder kernel, if any

In order to model the gas generation rate in interior ballistics calculations, powder burn rate is usually modelled as being proportional to the product of:
- the total exposed surface area of the kernel (usually a function of the fraction-burnt)
- the pressure, raised to some exponent
- the temperature, raised to some exponent
- an optional function of the fraction-burnt, to model the effects of diffused deterrents

(gosh time to stop.... this has wandered *way* far off of the original topic!!)

 

[Meph]

Do go on gentlemen.

 

[thebigslide]

Your two posts were awe inspiring. I'm reading them over a few times, fascinating!

One thing though, what about separating the two powders with a barrier that burns away? For example, a pouch or even a "wall" between the two charges made of a dacron-fluff like material that contains a powder, separating it from the other.

So this is something that is possibly feasible, but once combustion begins - anything loose is all pretty homogenized in there due to turbulance. Another issue that comes up when using loose powder is that the ignition source is at the base. It's less than ideal since the pressure wave is actually forcing the charge up towards the bore. You really don't want to toss a slow burning powder up into a large cavity and expose it to an ignition source.

Slower powders often have higher ignition energy requirements, but that's because they've used heavier deterrent coatings in order to give them a slow burn profile, not fundamentally because they are slower powders

I would add that this is advantageous and by clever design. Deterrent coatings are an important part of propellent design. Much less useful in pyrotechnics ;-) Ignition energy can be tested simply by slowly applying heat to a powder sample. The grains still burn from the outside in. The deterrent serves more, in combination with grain shape, to delay energy transfer from the surrounding combustion front to the combustable propellent within the grain. This is primarily a factor in ignition rather than combustion, though they are certainly related.

Also, I think your burn rate factor chart is upside down! Compare the grain size of H4198 with H335 for example and you will see that the H335 has more surface area per grain and a smaller grain size, yet has a much slower "burn rate" due to it's chemistry.

In propellent burn rate calculations I have seen, combustion temperature is usually something that can be masked by wrapping it up in enthalpy along with pressure since the heat loss due to soak is an unknown. A large, conservative error factor is prudently included. Firearms propellents may be a little different here. Programs such as quickload naively ignore this.

an optional function of the fraction-burnt, to model the effects of diffused deterrents.

This is something I don't have a lot of experience with. Can you recommend any papers on the subject? I am curious about the chemistry of typical deterrents and I really have little background in the design of typical modern deterrents and would like to know more.