The “Dart stability factor†is just the ratio of the “Aft leveraged area†divided by the “Fore leveraged areaâ€. The bullet is dart stabilized so long as the stability factor is greater than 1.0. But with a stability factor so close to 1.0, I would worry that some small material/machining deviation would reduce it to less than 1.0, making the bullet no longer dart stabilized.

Here is a non wasp-waist design, otherwise similar to the bullet shown above. Note that this one is NOT dart stabilized, as the stability index has dropped to below 1.0.

Next, I want to try a non wasp-waist with a tip made of lead instead of brass. This should move the CG foward, and increase the dart stability.

Here is a lead-tipped no wasp-waist bullet. Note that this moves the CG forward, and increases the dart stability index, and of course increases the bullet mass over the monometal design.

If you want to mess with it, pure tungsten has a mass density of 19.3 g/cc. I believe the easiest way to form it is to fill a mold with tungsten powder then add molten copper as a matrix. Or maybe they mix tungten powder and copper powder and fill the mold before heating to copper's melting point...

quote:

If you want to mess with it, pure tungsten has a mass density of 19.3 g/cc. I believe the easiest way to form it is to fill a mold with tungsten powder then add molten copper as a matrix. Or maybe they mix tungten powder and copper powder and fill the mold before heating to copper's melting point...

Available in 11" sticks suitable for machining...at the bargain price of $600 per stick!! Been there done that...

Just for grins, I ran one with a pure tungsten tip anyway:

Cal=45
Bullet seating depth=.322 in.
Bullet point radius=.5 in.
Total projectile length=2.391 in.
Metal changes at 1.500 in.
Rho before change=8.49 g/cc (brass)
Rho after change=19.3 g/cc (tungsten)
Bullet mass=1066.79 grains
CG at 1.330 in.
Aft leveraged area=1.249
Fore leveraged area=.6283
Dart stability index=1.988

Wow! Over 1000 grains with a dart stability index of almost two! I did not generate a picture, because all it would show is the CG moved up to 1.330 inches.

Almost makes you want to try firing one from a 410 ga smoothbore shotgun, and forget about spin stabilization...

What IF the bullet costs more than the gun...

Actually, I found another bug. But this simulation is accurate.

Before anyone relies on the previous wasp-waist results, better contact me and let me run them again, just to be sure.

Ain't SCIENCE grand?

Rob, the computer program is now accurate. If you want, I’ll be happy to run your 600 OVERKILL bullets, if you have interest. Fit them into the data above as best you can, and I’ll post a sample run. How long are they? No cutouts, I expect. Is a monometal brass used? Will the ½ inch point radius be OK, or do they look more “pointy†than these?

I just wrote a Gcode pgm for the waspwaist bullet that I'll probably have to adjust to get to 700grs. I will try it out next week.-Rob

Rob, what about forming a bullet seat on the front of a brass OVERKILL 45 cal then cramming a lead 38 cal slug into it to give the wasp-waist a little more front weight?

Rob, if this can be done, you would have a wide choice of 416 bullet grains and lengths to play with.

Henry- You'd have to swage the lead bullet into the brass cup for any chance of concentricity. You can then control any nose shape you want. That would require a second step and custom swaging dies would need to be designed. I'd probably machine in grooves to the cup so the swaged in lead bullet is ridgidly held in place. This would be a good approach for adding a tungsten carbide penetrator for example.-Rob

Rob, of course you are right about the more difficult technical issues of concentricity, rigidity, bonding the two dissimilar “bullets†together, etc. And mostly those are issues that you alone can solve: I won’t even pretend to be able to help, because I just simply lack the required experiences.

But the MARKETABILITY of the brass 45 OVERKILL wasp-waist “carriers†has occurred to me over the day today. So far, you seem to have worked pretty much alone in these developments, and THERE IS JUST SO MUCH LEFT TO TRY! Once you solve all the technical issues mentioned above, there is still SO MUCH left to try. All the various bullets, for instance, and all the various materials. By offering these brass “carriers†(the wasp-waist brass part, in various calibers) to shooters and handloaders, you can not only get help in wringing out all the possibilities. You can also be a single-source of carriers, swaging tools, etc. (at least for a while).

Sounds like a LOT of fun!

Tungsten is about 24% denser than tungsten carbide. Tungsten competes with depleted uranium in applications where high density is useful. Tungsten is also far easier to machine than tungsten carbide. Tungsten carbide is so hard that usually requires diamond tooling.

“http://www.atifirthsterling.com/tungstenheavyalloyproducts.aspâ€

Rob, I have no idea what the currently-accepted knowledge is about firing aluminum bullets. It may be so bad that you could only recommend this bullet be fired from 45 cal smoothbore rifles.

As you can see, it uses an aluminum wasp-waist “carrierâ€, rather than brass. BUT IT IS HIGHLY DART STABILIZED. This might be a good test vehicle for getting a handle on spin stabilization vs. dart stabilization.

Henry- My guess is a aluminum bullet would not hold the rifling even at low velocities. I've never seen one and to be honest never before had the capability to evn make one except one at a time. The swaged lead nose idea is quite doable and I've had a bit of experience with Hydraulic swaging of bullets with very good results. For years I made competition .223 bullets from fired .22LR cases and achieved incredibly good results. The advantage is the ease of changing nose shapes and penetration capabilities. Its also possible to swage a tungsten core into a lead bullet for dramtically increaded penetration. At these velocities, though, I'm not sure there would be that much advantage though. The foreward cup could be slit and then a pure lead tip swaged in place for low velocity expansion. Now that would be nasty. The grooves would be necessary for keeping the cup from becoming a sabot. -Rob

Aluminum bullets are good fun. These are .308" and we fired them just shy of 4000fps from a 30-06.

"http://www.gsgroup.co.za/winddrift.html"

G S Custom Bullets

“The actual mechanism of wind drift is interesting as it is often assumed that it is the result of wind blowing on the side of the bullet. In reality the bullet vectors (turns) into the wind within a short distance after exiting the muzzle. The stronger the wind, the more acute the angle the bullet assumes into the wind. The result is that the drag on the base of the bullet is then offset more to the downwind side of the bullet path and drags the bullet in that direction.â€

Once the bullet is free of the barrel, it “sees†only the local “apparent windâ€. This is the vector sum of the muzzle velocity and cross-wind velocity. If the bullet has a high dart stability, it turns in a direction so that it points into this apparent wind. At that time, the bullet is in a condition of symmetry with respect to the apparent wind, so I can see no way it could “feel†a steering force due to asymmetric drag on its base.

Here is a better explanation from "Rifle Accuracy Facts" by Harold Vaughn.

Gerard-I have no doubts that a aluminum bullet will reach amazing velocities. I admit to zero experience with them. Do they exhibit any accuracy at 100yrds? Do they hold the rifling? Any pics of recovered bullets. I'm very curious and Glad to see you posted the pics.-Rob

Rob,
Accuracy was no different from any other bullet and up to the capability of the rifle. I only shot them out to 200m because of the low BC. The trajectory after that was a joke. The pieces that I found, showed no indication of stripping the drive bands or jumping the rifling so stability was OK. This was part of a development towards a vehicle for a tungsten dart. You will notice the huge holes in the base of the bullets for that purpose. These ones, although a similar profile as a lead core 180gr bullet, only weighed 46gr. At the time we were only interested in seeing what the barrel would be like after a number of shots. To my surprise, accuracy remained good over a string of 40 shots and the barrel had no fouling that I could talk about.

Gerard- Now thats interesting and something I would not have predicted. I appreciate that. Did you fire for accuracy? What alloy did you use? Also what happened to the Tungsten dart idea? -Rob

I used a very ordinary rig to run the tests on the alu bullets and held under 2" at 100m. Used 6063 and 4x13mm and 6x20mm tungsten rods. 4x13 worked better. We poked holes in all sorts of stuff with them and, when we quoted price to the interested party, they lost interest. We shelved the project.

quote:

Originally posted by Gerard:
... I only shot them out to 200m because of the low BC. The trajectory after that was a joke ...

SD, the butt of so much satirical humor by Gerard, once again rears its "funny" head. No SD, no BC, no matter what the form factor.

How much did those 46-grain aluminum .308 bullets weigh when they had the tungsten rods in them? What was the velocity and BC like with the rods installed? A rough estimate on BC or simply a drop and velocity comparison would be greatly interesting, thanks in advance.

Henry,
Pretty much what Vaughn says, right?

RIP,

quote:

No SD, no BC, no matter what the form factor.

Absolutely so and who can argue the logic of that. Sd still has feathers to do with the probable penetration though.


The alu bullet with the 6x20 core was 160gr and the smaller core gave 105gr.

We did not do BC with the cores installed, only short distance penetration and accuracy.

I expect so, Gerard. I don’t have access to Harold Vaughn’s papers, other than that you posted.

I really appreciate your posts to this Thread. For the first time, I’ve seen where someone actually TRIED tungsten, and in aluminum carriers, no less! I expect we will have to jump around some on this side of the pond…

Does Vaughn suggest any studies of “dart stability� What you posted of his work generally applies in the cases I would call “high†dart stability.

"Rifle Accuracy Facts" by Harold R. Vaughn is a good read for anyone interested in the subject. It deals with conventional equipment and solutions to accuracy problems dealt us by everyday equipment. In order to illustrate the ordinary, he shows some ingenius solutions and routes to solutions. There are four copies available here.

Thanks, Gerard.
There is one less copy of the book at amazon.com now. I had missed out on that one.

Harold R. Vaughn is a "rocket scientist"/engineer who studied nuclear missile and artillery trajectories in professional life, eh? I can't wait to try to understand his electronic circuitry diagrams. Seems Precision Shooting will not publish just any old crank's ramblings.

I wonder if they would be interested in a piece about how little is known about the 400 Nitro For Black Powder 3" and more modern .395 caliber rifles?

Vaughn's book is indeed a must have for a gun crank.

Gerard, any special loading techniques/difficulties with the aluminum bullets, particularly in regards to the hollow base?

I tried hollow basing Barnes Mono RNs in the attempt to move the center of mass forward of the center of form for penetration stability.

But, when fired over typical charges of H4895 in my Lott, the cases evinced flattened primers and ejector slot extrusion accompanied by heavy bolt lift. I quickly abandoned that idea assuming I'd created a Minie' ball effect and some sort of increased bullet drag in the barrel.

“Golfsmith Tungsten Powder 1/2 Poundâ€

“http://www.golfsmith.com/ppage.php?stynum=9466&lcode=CI&cm_mmc=froogle-_-consumer-_-1-_-r&ci_src=14110944&ci_sku=9466&tcode=fr_home#â€

Or Google [“tungsten powder†$].

This place sells ½ pound of tungsten powder for $19.00. They use it to add weight to golf clubs.

I was thinking you could leave a “cup†on the forward end of a carrier (either brass or aluminum), and instead of cramming a bullet into it, you could pour it full of tungsten powder. Then heat the bullet and drip some paraffin on top of the powder, to keep the powder from moving around.

quote:

can't wait to try to understand his electronic circuitry diagrams

He shows a nifty pair of devices to test bullet concentricity and not dificult to build at all.

PWS, the only thing different about alu bullets to me was the amount of fast burning powder they required. The absence of fouling was also worth noting. I did not have any indication of expansion of the base of the bullet due to the hole drilled from the base, but then I also had no base line for comparison as you had. Maybe the fact that those that we fired without cores, were drilled with 4mm holes and left enough thickness on diameter to withstand expansion. They departed with little resistance, having drive bands and weighing only 46gr. That would also play a role in reducing the probability of expansion of the base / boat tail area.

I believe the folks at Corbin Swaging have a procedure to produce tungsten powder/lead or tin mixes and swage them into a sintered/solid projectile under a few tons of pressure.. I'll have to give Dave a call and confirm or at least check my inorganic eutectic mixture charts and see what does what. I'm not at all surprised by the high pressure effects of skirted bullets in a big bore. Reducing the charge will solve that problem.The aluminum bullet/tungsten core approach sure is interesting though. Kinda completely at the opposite end of the Subsonic heavy bullet approach. -Rob

Rob, I hope I’m wrong, but I don’t think you’ll find any tungsten-lead eutectics. Maybe tungsten-copper, but about 2,600 C is the lowest melting point eutectic, I think.

Here is a patent claiming success in mixing tungsten powder into melted lead/tin eutectic with “vigorous stirring†(yeah, I’ll bet!). But it looks like a pretty good process, using only 10,000 psi ram pressures and metal up to about 17 g/cc. Apparently the tungsten powder stays in its original form, but the interstitial spaces get filled with lead/tin.

“http://www.freepatentsonline.com/5279787.htmlâ€


I was trying to find you some highly dart-stabilized shapes which did not require the wasp-waist extra machining, and that is when I hit on the “barrel-burner†very light weight aluminum bullets… But, for subsonic shooting, I too want the HEAVY bullets. But I think I want highly dart-stabilized, too.

This is about as close as I can get computing this REALLY HIGH dart stability projectile. It uses a standard 400 gr. 416 cal bullet available from Midway, carried in an aluminum carrier. I showed a 0.322 in. bullet seat, but this could obviously be increased if more aluminum is desired to hold the rifling.

NOTE THIS IS NOT A WASP-WAIST!

I hope the 416 bullet will allow enough room inside the limited ridge-rider diameter for a proper seat for the 416 bullet within the aluminum carrier. If it does, this could really be an exciting, highly dart-stabilized projectile!

Wow, I understood about 0 posts of page #4.

A .396/410gr LBT LFN GC cast boolitt would work better, and you would not even need the GC. More wall thickness in the aluminum carrier to grip the bullet, an extra 10 thou per side.

Or how about a .375/350-grain? Heavy enough?

Corbins

Rob had previously mentioned Corbin’s bullet swaging, and its pretty apparent that they are a leader in using tungsten powder for bullet making.

To form bullets with high dart stability, it is very important to move the bullet’s center of mass as far forward as possible. The easiest way to accomplish this is to use very light materials (aluminum?) in the back end of the bullet and very heavy materials (tungsten?) in the front end.

A simple way to visualize this is to imagine that the situation were reversed, and that the very heavy materials were used in the BACK of the bullets and the very light materials were used in the FRONT of the bullets. Then, as the bullet flies, it is being “pushed†along by the heavy weights in its ass-end. These heavy weights constantly threaten to “come around†or swap ends with the light materials up front. This is inherently unstable.

Gerard has, previously in this Forum, revealed his success with 6061 aluminum (a “free machining†alloy) in bullet making, so probably this is a very good way to build the back ends of the bullets. If a cavity is machined into the bullet’s front end, this cavity can be filled with tungsten powder. The powder is then compressed by a ram to remove most of the entrained air. A lead plug can then be forced into place, both to prevent the tungsten from shifting around during handling/firing, and to provide a streamlined “point†for the bullet. Tungsten, being almost twice as dense as lead, offers about the best way to move the center of gravity as far forward as possible.

Such bullets are inherently dangerous as the always travel tip-forward, even during free-fall. I have no doubt that such a bullet, if dropped from a height of about 3,800 feet, would break the sound barrier just as it hit the Earth. And be traveling tip-first. So don’t fire them straight up, and expect air-resistance to cause them to fall safely back to Earth.

On the other hand, a cluster of enemy soldiers, hiding behind a thick wall but without sufficient overhead cover, would hardly expect to be hit from overhead by a rain of 500-grain supersonic darts falling from a clear sky.

How about threading the base of a solid shank bullet design like the barnes or tbbc or to save money use screws or make a custom screw for the aluminium "Dart"

Maybe a knurled edge flat nose conical solid with a threaded shank.

Or just buy bulk screws that will be good enough for plinking.