Best known BC, any caliber

[dareposte]

The highest I've found is 0.891 (Berger 300gr VLD .338) Any higher?

 

[RAW968]

Re: Best known BC, any caliber

If I remember right... 50BMG 750gr A-Max 1.05

 

[jrob300]

Re: Best known BC, any caliber

According to their website, GS Customs make a 566 gr bullet for the 460 Steyr with a BC of 1.085. They also make a 295 in .338 with a BC of 1.010.

John

 

[desertHK]

Re: Best known BC, any caliber

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: RAW968</div><div class="ubbcode-body">If I remember right... 50BMG 750gr A-Max 1.05 </div></div>


Since we are going with the 50 BMG cal, the Lehigh 800 grains solid match hybrid .510 cal has a BC of 1.124.

 

[desertHK]

Re: Best known BC, any caliber

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: RAW968</div><div class="ubbcode-body">If I remember right... 50BMG 750gr A-Max 1.05 </div></div>

That's manufactured BC. Real data is a bit closer to .97-.98 I believe.

 

[ewoaf]

Re: Best known BC, any caliber

this again?......
*sigh*

http://www.vincelewis.net/dora.html

7 to 8 ton shell

Rate of fire, 2 rounds per hour

Caliber 80cm ( 800 mm or 2ft 8in approx )

The shells for Dora and Gustav, including the 1 ton charge was 17 feet long. It needed a ton of charge to send the 7 ton shell over 25 miles from the 100 foot long barrel. The shell on test firing proved to be able to penetrate 30 feet deep into earth making a crater over 90 feet feet across.

The velocity of the shell was 2,700 feet per second, the barrel had a life of about 150 rounds.

The barrel weighed 400 tons and the breach block where the shell was inserted weighed over 100 tons Dora stood 4 stories high, over 20 feet wide 141 feet long and weighed 1323 tons.

 

[hammerhead]

Re: Best known BC, any caliber

Here's what 7 tons of BC looks like.........

 

[redbullitt]

Re: Best known BC, any caliber

I think the barrel life on those big guns and railway guns were like 70 rounds before they needed to be re lined lol... gotta be sparing with those sighters

 

[Moose72]

Re: Best known BC, any caliber

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: hammerhead</div><div class="ubbcode-body">Here's what 7 tons of BC looks like.........

</div></div> That's what my chipmunk bullets look like..

 

[tigerhawk]

Re: Best known BC, any caliber

The .375 Viersco Magnum, if it ever actually gets produced for sale, is said to have a 414 grain bullet with an ESTIMATED BC of 1.25-1.27.

 

[Emouse]

Re: Best known BC, any caliber

maybe take a look at the experimental extreme VLD's produced for the early CETME rifle and NATO cartridge? These where aluminium and took there shape from Voss rocket technology?

 

[dareposte]

Re: Best known BC, any caliber

Sorry I forgot to specify.. shoulder fired and legal for civies in the USA

 

[Fred_C_Dobbs]

Re: Best known BC, any caliber

I'd bet a month's beer money the highest BC ever is the DU penetrator from a M829 120mm APFSDS.

It weighs 9.41 lbs, is 0.6" in diameter and 19" long. Cd @Mach5 is 0.4988. Frontal area is 1.824146925x10^-4 m^2. Maybe someone can convert that to G1??? ;-)

What about the .416 Barrett and .408 Chey-Tac? Are there no heavy (750-gr+) bullets for them? With the same weight and a smaller caliber, I'd think their BC would be even higher than a .50 BMG.

 

[JL]

Re: Best known BC, any caliber

M829 weights 9.41lbs, and it has 31,7:1 lenght to diameter ratio accordingly to numbers you mentioned.

Internet says that German Rheinmetall DM53/DM53A1/DM63 penetrator weights 11 lbs and has 38:1 lenght to diameter ratio.

IMI M-338 has tungsten (denser than uranium) penetrator, so its very close if not heavier than both M829 and DM53.

I prefer Lager

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Fred_C_Dobbs</div><div class="ubbcode-body">I'd bet a month's beer money the highest BC ever is the DU penetrator from a M829 120mm APFSDS.

It weighs 9.41 lbs, is 0.6" in diameter and 19" long. Cd @Mach5 is 0.4988. Frontal area is 1.824146925x10^-4 m^2. Maybe someone can convert that to G1??? ;-)
</div></div>

 

[Fred_C_Dobbs]

Re: Best known BC, any caliber

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: JL</div><div class="ubbcode-body">M829 weights 9.41lbs, and it has 31,7:1 lenght to diameter ratio accordingly to numbers you mentioned.

Internet says that German Rheinmetall DM53/DM53A1/DM63 penetrator weights 11 lbs and has 38:1 lenght to diameter ratio.

IMI M-338 has tungsten (denser than uranium) penetrator, so its very close if not heavier than both M829 and DM53.

I prefer Lager

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Fred_C_Dobbs</div><div class="ubbcode-body">I'd bet a month's beer money the highest BC ever is the DU penetrator from a M829 120mm APFSDS.

It weighs 9.41 lbs, is 0.6" in diameter and 19" long. Cd @Mach5 is 0.4988. Frontal area is 1.824146925x10^-4 m^2. Maybe someone can convert that to G1??? ;-)
</div></div> </div></div>
Sorry, I'm a PBR man.

How odd. Begs the question why the US uses the tungsten penetrator in their practice rounds but DU in the angry variety.

I did check, BTW, and was surprised to learn tungsten is denser than DU. So until someone makes an osmium penetrator, I reckon tungsten is king dog shit.

 

[maladat]

Re: Best known BC, any caliber

From Scientific American article "The Science of the Silver Bullet" (http://www.scientificamerican.com/article.cfm?id=the-science-of-the-silver):

<div class="ubbcode-block"><div class="ubbcode-header">Quote:</div><div class="ubbcode-body">
Despite the recent attention, depleted uranium is not all that new. The military has experimented with it since the 1970s. Military interest in the heavy metal is twofold: For one thing, uranium is almost twice as dense as lead, and thus packs a lot of punch as ammunition. Like its slightly denser cousin, tungsten, uranium can penetrate most heavy armor. But whereas tungsten projectiles become rounded at the tip upon impact, uranium shells burn away at the edges. This "self-sharpening" helps them bore into armor. </div></div>

DU is better.

 

[darrindlh]

Re: Best known BC, any caliber

I think that the chey tac 355grn bullet has a bc of 1.01
Thank you
Darrin

 

[TresMon]

Re: Best known BC, any caliber


BC is not everything. Angle of repose can get so bad on "high bc" bullets that your working backwards. Only go by real field generated BC, & though rare doppler radar being preferred.

 

[ply1951guy]

Re: Best known BC, any caliber

Tres, I am curios how the BC affects the angle of repose? I was not aware of any connections between BC and angle of repose. Can you elaborate on that some more.

 

[TresMon]

Re: Best known BC, any caliber


I'm no ballisititician nor can I spell it, but generally to get bc numbers up the bullet has to get longer for a given caliber. And the longer the bullet the further the the distance between the center of the bullets mass and the center of pressure on the bullet. This induces the angle of repose, if i'm explaining it correctly. Refer to the back of your Sierra load manual. So super long needle like bullets would practically be flying so out of alignment that it would be "crabbing" in the wind and with the calculated bc would considerably higher than real world BC.

bullets don't fly pointed perfectly the direction they are traveling. It's angle of respose that causes them to fly a ***LITTLE*** sideways. better said they fly out of alignment. Longer bullets equal more out of alignment flight. So their is a delicate balance between making a bullet ultra sexy but not getting AOR to rediculous levels

 

[groper]

Re: Best known BC, any caliber

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: TresMon</div><div class="ubbcode-body">
I'm no ballisititician nor can I spell it, but generally to get bc numbers up the bullet has to get longer for a given caliber. And the longer the bullet the further the the distance between the center of the bullets mass and the center of pressure on the bullet. This induces the angle of repose, if i'm explaining it correctly. Refer to the back of your Sierra load manual. So super long needle like bullets would practically be flying so out of alignment that it would be "crabbing" in the wind and with the calculated bc would considerably higher than real world BC.

bullets don't fly pointed perfectly the direction they are traveling. It's angle of respose that causes them to fly a ***LITTLE*** sideways. better said they fly out of alignment. Longer bullets equal more out of alignment flight. So their is a delicate balance between making a bullet ultra sexy but not getting AOR to rediculous levels

</div></div>

Largely true for a traditional design spin stabilized projectile... Its alot more complicated when you look into the mechanics of it and these generalizations only apply to average bullet designs, which is pretty much every bullet since they are essentially all of similar design, shape and density.

With a different design to the norm, you can make a projectile longer, with less spin requirement and more stability if you address the mechanics more directly rather than just looking at the overall length.

Without giving any more details, and im reluctant to show a picture of these new projectiles, im predicting the highest BC ever seen in a small arms caliber rifle projectile. Ill post all the details once ive finished testing them. Watch this space...

 

[USGUNWORKS]

Re: Best known BC, any caliber

tag

 

[ply1951guy]

Re: Best known BC, any caliber

Tres, thanks for the explanation. I am not ballisitician either, but I understand your explanation. The shape of the ogive has a large effect on where the CP of the bullet lies. The angle of repose is something that not a lot of people understand, but it is important during flight.

groper... PM inbound.

 

[JL]

Re: Best known BC, any caliber

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: maladat</div><div class="ubbcode-body">
DU is better. </div></div>
Topic was about BC, not terminal effects after impact...
Same dimensions and shape but denser material means better BC.




About rifle projectiles, this is the best design I know if only talking about BC:

In 1888 shot from Mauser rifle, MV for 167gr bullet was 2362fps. At 2000meters, or 2187yds velocity was still 1673fps. THAT is something. G1 BC has to be over 1.5 in order to get that kind of terminal velocity.

Penetration was also excellent, 5mm caliber sabot version penetrated 6.7feet thick dry pinewood wall. Problems were accuracy and particulary wind. But BC is good.

Others have tried that later too, but never successfully.
7.62 "Kill-a-Kong" -bullet is one. Shorter tubes were used in .44 and .38 revolvers, apparently in south-africa. They never broke thru, but terminal ballistics were still scary.

 

[groper]

Re: Best known BC, any caliber

And how do you suppose they determined the velocity back in 1888? i can see several problems with this early design...

But, tubular projectiles have been used successfully, as in recent times.

The problem is once they slow down to about mach 1.6, the way the pressure waves interact renders them aerodynamically similar to a giant flat nose solid and VERY high drag thereafter. in other words, range limited.

They were developed/refined in recent times for use in AA guns with the advantage being reduced time of flight. They work very well with very low drag above mach 1.6 and because they are hollow and light, they can be driven at high Muzzle velocities for a very flat trajectory until they reach mach 1.6. In the case of the 30mm AA training round pictured, about 2100m.

 

[JL]

Re: Best known BC, any caliber

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: groper</div><div class="ubbcode-body">And how do you suppose they determined the velocity back in 1888? i can see several problems with this early design...</div></div>
Ballistic pendulum, I guess. Wasnt there tho.
System was invented in 1742 by English mathematician Benjamin Robins.

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: groper</div><div class="ubbcode-body">
But, tubular projectiles have been used successfully, as in recent times.
The problem is once they slow down to about mach 1.6, the way the pressure waves interact renders them aerodynamically similar to a giant flat nose solid and VERY high drag thereafter. in other words, range limited.

They were developed/refined in recent times for use in AA guns with the advantage being reduced time of flight. They work very well with very low drag above mach 1.6 and because they are hollow and light, they can be driven at high Muzzle velocities for a very flat trajectory until they reach mach 1.6. In the case of the 30mm AA training round pictured, about 2100m. </div></div>

Yep, they have been used and tried in various large caliber systems. According to my source, offical initiative about tubular rifle bullet testing was made by US-Army as well in early 70´s, but budget cuttings (Vietnam) killed project before it even started.


Anyway, bullet principle was invented by Böhmen (nowday part of Czech rebublic) gunsmith Karel Krnka (or maybe his father Sylvester Krnka). German professor Hebler did Further development of cartridges, paper sabots and loads.

Same idea at about same time was tested by Arman Mieg too.
Mieg joined the Bavarian army in 1859. He became commanding officer in 1872 as captain, and was in military shooting school in Spandau. At 1889 he was awarded by Prussian war ministry, thanks to developement of infantry rifle 1888.


So tubular bullets were tested and developed by offical organisations as well. Secondly, large caliber projectiles are not comparable to small ones.
I dont know much about aerodynamics, but I do know what difference big and small Reynold´s number will make in practice.

All saboted bullets are still suffering exactly same problems than 100 years ago. Poor accuracy. Constant sabot separation is virtually impossible to achieve with tiny scale parts.
50cals and up are different story.
Another problem would be wind drift, even if sabot problem would be solved. But this topic was all about high BC itself, thought why not to mention about old idea.

 

[groper]

Re: Best known BC, any caliber

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: JL</div><div class="ubbcode-body">
Ballistic pendulum, I guess. Wasnt there tho.
System was invented in 1742 by English mathematician Benjamin Robins.</div></div>

My ploy was that i doubt the velocity data you quoted was anywhere near accurate, especially for the design depicted in the picture you posted.


<div class="ubbcode-block"><div class="ubbcode-header">Quote:</div><div class="ubbcode-body">
All saboted bullets are still suffering exactly same problems than 100 years ago. Poor accuracy. Constant sabot separation is virtually impossible to achieve with tiny scale parts.
50cals and up are different story.
Another problem would be wind drift, even if sabot problem would be solved. But this topic was all about high BC itself, thought why not to mention about old idea.

</div></div>

Not true, there was nothing wrong with the accuracy of the MODERN tubular projectiles, in fact they were more accurate than conventional projectiles. As i said, the problem lies within the limited range. The concept was abandoned in favour of the kinetic energy on target, terminal performance and payload potential of a conventional projectile with respect to the intended targets (being aircraft).

That old design you depicted, they had no idea of what they were doing with respect to supersonic flows and wave drag back in those days. The internal and external angles were not optimized and had no chance of getting it right with their limited knowledge not to mention the drive bands, sabot and obturation integration.

The modern tubular projectile has a drag coefficent about half what a normal VLD projectile has until about mach 1.8 when it all goes bad REAL QUICK thereafter.

 

[JL]

Re: Best known BC, any caliber

I dont want to turn this interesting topic into yes/no argument. I have no experience shooting tubular bullets whatsoever. Also, I dont meant to question your knowledge with bigger sabot/tube projectiles. English is my third language, just want to clear out these points. Sometimes my translation result is curious or even rude, unintentionally.

I still have feeling that we are partly talking about different things. You talk about bigger guns, Im talking about .30 cal / 5-8mm projectiles.

Firstly, when I mentioned saboted ammunition accuracy problems, I mean small rifle calibers "Under .50cal" ,as I said.
Only smaller sabot system in military use I´m aware of is is Swedish PSG90 -sniper rifle ammo, and its problem is inaccuracy too. But idea is to compensate it with smaller drop when exact range is not known or there is no time to define it.
So if there is a working sabot system for small rifle calibers nowdays , I haven´t heard about it. Feel free to share manufacturer/model if you know one.

What comes to that old design and drive bands, original text mentions that copper drive band was used in early designs with steel projectile, but later version (as in pic) did not need it since sabot was touching and did same thing.
And I would not laugh to shape too much either. They did not have fancy computers, but still managed to get shape right:


This is Sears-Haack shape from 1947, which (still) produces lowest theoretical wave drag in supersonic area.

If you compare it to tubular bullet silhouette designed about 60 years earlyer- by the men who "<span style="font-style: italic">had no idea of what they were doing with respect to supersonic flows</span>", as you described their knowledge. They weren't too far IMO. Gotta respect old trial-error method.

Tubular bullet needs always sabot, as it did hundred years ago.
I have no access to big manufacturers R&D departments or military applications- but small caliber sabots aren't working at the moment. As they didn't 100 years ago. Latest commercial trial and failure was done by Winchester in late 90´s or so- "Accelerator" was name of sabot cartridge if I recall correctly. And same inaccuracy was still a problem.

What comes to tubes in SMALL bullets and supersonic airspeed- I know that modernized version of that design has been simulated with high-end design softwares year-two ago. Results were, modestly said, very promising. Guy who did it is a member of SH, but I wont tell any details of that test. He may tell it if he wants.

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: groper</div><div class="ubbcode-body"><div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: JL</div><div class="ubbcode-body">
All saboted bullets are still suffering exactly same problems than 100 years ago. Poor accuracy. Constant sabot separation is virtually impossible to achieve with tiny scale parts.
50cals and up are different story.
Another problem would be wind drift, even if sabot problem would be solved. But this topic was all about high BC itself, thought why not to mention about old idea.

</div></div>

Not true, there was nothing wrong with the accuracy of the MODERN tubular projectiles, in fact they were more accurate than conventional projectiles. As i said, the problem lies within the limited range. The concept was abandoned in favour of the kinetic energy on target, terminal performance and payload potential of a conventional projectile with respect to the intended targets (being aircraft).

That old design you depicted, they had no idea of what they were doing with respect to supersonic flows and wave drag back in those days. The internal and external angles were not optimized and had no chance of getting it right with their limited knowledge not to mention the drive bands, sabot and obturation integration.

The modern tubular projectile has a drag coefficent about half what a normal VLD projectile has until about mach 1.8 when it all goes bad REAL QUICK thereafter. </div></div>

 

[groper]

Re: Best known BC, any caliber

read this if you want to know more about the modern, properly designed tubular projectiles
--> http://www.dtic.mil/cgi-bin/GetTRDoc?AD=ADB087370&Location=U2&doc=GetTRDoc.pdf

Also, you may not know, that it is impossible to spin stabilize a complete sears/haack body of revolution that you depicted, this is why you never see a projectile with a long tail. It is also the reason i can pretty much guarantee that early hollow projectile that you also depicted, would not have flown at all, let alone 2000m... it simply would not have stabilized due to its shape, and the internal air passage would have been in a "choked" flow state to be an effective tubular projectile regardless... dont believe everything you read...

 

[maladat]

Re: Best known BC, any caliber

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: JL</div><div class="ubbcode-body"><div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: maladat</div><div class="ubbcode-body">
DU is better. </div></div>
Topic was about BC, not terminal effects after impact...
Same dimensions and shape but denser material means better BC.</div></div>

I understand that the general thread topic is BC.

However, I was attempting to address the question in the post prior to mine about why the US military uses depleted uranium projectiles in war but tungsten projectiles for practice despite tungsten being marginally more dense (about 1%). The answer is that depleted uranium is much better for armor penetration.

 

[SRT_Supply]

Re: Best known BC, any caliber

So the real question I have left is, why can't we figure out a way to increase effective bullet mass without increasing volume, by replacing lead with tungsten? If I understand the numbers correctly, shouldn't you be able to effectively increase the bullet weight by about 40-50%? It might be prohibitively expensive, but somehow I suspect there's still people out there willing to pay it for something significantly better.

Or will the greater mass not have an appreciable influence upon the exterior ballistics?

 

[bohem]

Re: Best known BC, any caliber

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: SRT Supply</div><div class="ubbcode-body">So the real question I have left is, why can't we figure out a way to increase effective bullet mass without increasing volume, by replacing lead with tungsten? If I understand the numbers correctly, shouldn't you be able to effectively increase the bullet weight by about 40-50%? It might be prohibitively expensive, but somehow I suspect there's still people out there willing to pay it for something significantly better.

Or will the greater mass not have an appreciable influence upon the exterior ballistics? </div></div>

Bullet mass is directly linked to the BC. The cost of such a bullet is prohibitive generally because of the incredibly high price of W vs. Pb

Your average retail cost of a Pb and Gilding metal jacket type 7mm heavy VLD is about $0.40-$0.45, figure it's going to cost about 2-2.5x's that for the cheapest route in Tungsten.

Next you have to figure that we're already pushing cases to the max to wring velocity from them, so are you willing to shoot a 260gr 7mm VLD from a 7 WSM at 2400 fps? If you're shooting ELR distances you're already using a lot of the internal adjustment of the scope to get there, you're going to have another problem next. Getting a scope that has 200 MOA of internal adjustment so you can shoot 2200yd with that 260gr 7mm VLD.

Or, you can keep the bullet mass the same and make improvements to the aerodynamic shape to reduce the form drag. Then your regular 160-180gr bullet in 7mm will have a significant increase in efficiency, it will shoot flatter with less wind drift, you can use the existing equipment to do it (or go even harder with those cool looking Bartlein gain twist barrels for a more aggressive shape).

The AOR mentioned above causes problems, going super heavy in standard shapes causes problems, the tubular bullets thrown with a sabot causes problems... Everything is a trade off, if there was a magic setup it would be done already.

The reason that you can get sintered tungsten cores and monolithic solids and heavy jacketed type configurations is because there are lots of people thinking along this line and working to improve the mouse trap.

 

[groper]

Re: Best known BC, any caliber

you can already buy bullets with tungsten in them, barnes MRX springs to mind immediately but there are others... everything has already been done at one point or another... whether or not its worth it, is in the the eye of the beholder...

 

[jrob300]

Re: Best known BC, any caliber

I'm just guessing here... but I'd conjecture that we've violated the original intent of this thread a while back... our OP seems to have left the building.

John

 

[JL]

Re: Best known BC, any caliber

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: groper</div><div class="ubbcode-body">
Also, you may not know, that it is impossible to spin stabilize a complete sears/haack body of revolution that you depicted, this is why you never see a projectile with a long tail. </div></div>

And why is that exactly in your opinion?

 

[Cmonroe]

Re: Best known BC, any caliber

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: tigerhawk</div><div class="ubbcode-body">The .375 Viersco Magnum, if it ever actually gets produced for sale, is said to have a 414 grain bullet with an ESTIMATED BC of 1.25-1.27. </div></div>

That should have never been posted the BC is higher, lol.

 

[groper]

Re: Best known BC, any caliber

The answer is poor stability, thats why.

Without going into great detail as projectile stability is a very complex tpoic that requires alot of prior knowledge to understand it well.

Spin stabilized projectiles as we know them, have a center of gravity behind the center of pressure. A typical rifle projectile design will have the center of gravity pretty damn close to 60% of its length from the bullet tip. The center of pressure, typically lies around the 33% mark. This difference is called the overturning moment, and acts to turn the bullet over rather than fly point first. This make them "inherrrently unstable" or statically unstable, so without some other force they wont fly point first and simply tumble. A rifle uses spin to gyroscopically stabilize the projectile, and the gyroscopic force must be greater than the overturning moment, thus your minimum twist requirements for a barrel/projectile combination for it to be stable.

The static stability of a projectile relates to a number of things including center of gravity, center of pressure, normal force (which acts on the center of pressure), axial and transverse moments of inertia, radii of gyration, air density etc.

Dynamic stability is another type of stability again and how can i put this... it relates to a projectiles ability to return to normal flight if its attitude is upset, rather than amplify it. Factors affecting it include, magnus moment, angle of attack, damping moment etc.

Now, what happens when you increase the length of a typical boat tail, or make a projectile with a very long tail like in the picture you depicted, is you destabilize it in many ways. These are;

1. Increased Magnus moment, which increases the overturning moment. If the CoG was in front of the CoP,as opposed to behind it, then the magnus would act to increase stability rather destabilize it. This means less dynamic stability.

2. Increased transverse to axial inertia ratio. Because the projectile is longer, with more mass about its ends rather than its axial extremities (ie nearest the bullet jacket), it has more transverse inertia and less axial comparitively. So it requires a faster spin rate to achieve the same gyroscopic stabilization as you have reduced this ratio. It also means the spin decays quicker during flight and a projectile can destabilize down range, despite it being stable at the muzzle. A virtually nonexistent phenomenon with our typical modern balanced designs as normally the reverse is true- they get more stable down range. This means less static stability.

3. Reduced pitch damping moment from the more symmetrical shape, nose to tail. The difference between the angle of attack and normal force generated by the nose and boat tail become closer in magnitude to each other. So when a projectile begins to yaw, the amplitute has greater tendency to cyclically increase rather decrease and this means less dynamic stability.

4. Drag, related to the above point in the same manner, the base drag acts to stabilize the projectile by acting on the opposite side of the CoG from the CoP. So the base drag actually acts in a moment that fights the normal force in front of the CoG. So if you reduce the base drag, which you will from a small cross section tail, you also reduce static and dynamic stability.

There are more issue at play also, but i grow weary from typing at this point, so what it all boils down to is this;

In a COMPLETE sears/haack minimum wave drag body, cannot be spin stabilized because there are more destabilizing forces acting upon it than can be overcome by the gyroscopic force in a practical application. If you could somehow spin the projectile at an incredible rate, without increasing the velocity and therefore the other forces, then in theory it could be done. Imagine having a 1:1 twist barrel for example, its simply not going to happen...hasnt happened...and will never happen...

 

[dareposte]

Re: Best known BC, any caliber

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: jrob300</div><div class="ubbcode-body">I'm just guessing here... but I'd conjecture that we've violated the original intent of this thread a while back... our OP seems to have left the building.

John </div></div>

Nope still here, a bit fascinated by the tubular designs.

 

[groper]

Re: Best known BC, any caliber

dont know what the BC is... but its way up there...

 

[Emouse]

Re: Best known BC, any caliber

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: groper</div><div class="ubbcode-body">you can already buy bullets with tungsten in them, barnes MRX springs to mind immediately but there are others... everything has already been done at one point or another... whether or not its worth it, is in the the eye of the beholder...</div></div>

Yes,..DRT make "conventional" high BC vld's using tungsten powder. These are well documented in Litz's book.

CORBIN has been advocating this and supplying tooling for quite a while.

 

[RTH1800]

Re: Best known BC, any caliber

Shot an electric fence post out of my .308 Win once! That was about 40" long. I think that was the winner.

 

[Augustus]

Re: Best known BC, any caliber

Gentlemen, The ZA .375 7.0 cal demonstrated a drop measured BC of 1.2 at 2550 fps over a distance of 1020 yds. This is where it is stable from an 8 twist. I fired it at 2700 from a 6.5 twist and had sub-1/2 min accuracy at 300 yds. I did not check the drops at distance because I was running short of projos and wanted to see how they handled higher velocities. I pushed it to 2850 and it was showing signs of becoming unstable. I have a 5.5 twist on the way and it should be stable to 2900. Anyway here is a bullet BC 1.2 at 2550 over the distance of 1020 yds. I expect the BC to be higher over the same distance at 2900. The 6.5 cal. 400 gr has a drop measured BC of 1.1 or so at 3050fps over a distance of 1020 yds. It also demonstrated a BC of 1.025 over a distance of 2560 yds at 3050fps.