AeroSpike Bullets

[HappyHellfire]

Maybe I am a little slow, but wouldn't your velocity comparison graph be a little more informative if both bullets had the same muzzle velocity? It is not real clear to me whether the difference between the two velocities curves is due to differing drag coefficients or muzzle velocity.

In the velocity comparison plot are these measured or modeled velocities?

Good question. I am comparing the Sierra 168 data from McCoy's External Ballistics and used the MV that is given for that round. For the Aerospike I am using the MV that was measured with 44 grains of IMR 3031.

This comparison if from a trajectory simulation that I wrote. For the Sierra 168 I used McCoy's data, for the Aerospike I used the design data that I have.

 

[HappyHellfire]

Thanks for all of the great questions. I was getting burned out working on this alone and thinking that no one would be interested in it.

My biggest take away is that y'all would want to see proven accuracy data. I have a sub MOA AR-10 that I can use for that. I have enough material to make a couple hundred more prototypes and I can start playing with the load and seating to see how accurate I can get it.

While I'm doing that , I'm also working on a newer version. This one will have a R7 secant ogive. If my modeling is right (and it has been so far) I think I can get a drag coefficient of less than 0.2. That would be insane!

 

[Taylorbok]

They look cool that's for sure but ya I think your target consumer would be ELR shooters. I haven't seen a solid 30 cal bullet that claims to outperform a 245 berger or 250 a-tip and you can run them in slower twist barrels.

If you are targeting ELR shooters I would consider 338 and larger sizes, run the numbers and see what you can come up with, and then find someone who will shoot them for you.

 

[HappyHellfire]

They look cool that's for sure but ya I think your target consumer would be ELR shooters. I haven't seen a solid 30 cal bullet that claims to outperform a 245 berger or 250 a-tip and you can run them in slower twist barrels.

If you are targeting ELR shooters I would consider 338 and larger sizes, run the numbers and see what you can come up with, and then find someone who will shoot them for you.

Thanks for the input. I'm really only using a .308 because I have a single shot H&R in that size and prototyping bullets can be dangerous. Also the best data I have to compare to comes from the Sierra 168 in .308.

What I want is a .50 to play with on a 2000 meter range. Oh the damage I could do with that. The bigger bullets are easier to stabilize. Maybe one day.

 

[BartsBullets]

So I ran the numbers and it is a no-go with a 13.5 twist 6mm. The Sierra HPBT drops from a stability (Sg) of around 2.5 @ Mach 2.5 at 10 inches to around 1.5 with a 13.5. My bullets in that caliber at that twist would be around 0.6. I could probably design one but it would be a while.

Do you want some of the .308 that I have already tested? Those have a Sg around 1.9 at Mach 2.5.

Not much of a 308 type guy. I’ll standby for the short range 6MMs. Or make some 103 to 105 gr 6mm for 8 twist.

Bart

 

[Alan Warner]

Not much of a 308 type guy. I’ll standby for the short range 6MMs. Or make some 103 to 105 gr 6mm for 8 twist.

Bart

Bart;
Your never going to see a 6mm solid in those weights that will work in an 8 if it's anything close to a long range design. More like 6 --maybe.. 7 might be marginal.

Alan

 

[BartsBullets]

Bart;
Your never going to see a 6mm solid in those weights that will work in an 8 if it's anything close to a long range design. More like 6 --maybe.. 7 might be marginal.

Alan

It’s up to HappyHellfire to figure out how to make them. I have the equipment to test them. It’s a big hill to climb to just shoot as good as what we have now.
Bart

 

[geo.ulrich]

I posted some pictures of bullets I made like this from copper and lead on the forum a few years ago. if I can find them or if I even still have them I'll post again.... I'll just say the longer bt length creates stability PROBLEMS....

 

[std7mag]

My worry is a wobble induced from the tail.

But, hey!
If he can come up with some 90gr, 25 caliber bullets, i'm your huckleberry for testing!

 

[HappyHellfire]

I posted some pictures of bullets I made like this from copper and lead on the forum a few years ago. if I can find them or if I even still have them I'll post again.... I'll just say the longer bt length creates stability PROBLEMS....

That was the same thing that ARL found. The longer BT moves the center of mass back and the increased base pressure moves the center of pressure forward. This causes the overturning moment to increase and decreases stability.

The AeroSpike has the same problem only not as bad. That is why I can't use an R10 secant ogive on monolithic bullets. I have to keep the center of pressure as far back as possible because the aerospike moves it forward a lot.

Stability is linearly related to density (sectional density in the case of jacked bullets). If I can get them accurate and stable in copper then it is guaranteed that when I eventually shift to lead core it will be stable.

 

[HappyHellfire]

My worry is a wobble induced from the tail.

But, hey!
If he can come up with some 90gr, 25 caliber bullets, i'm your huckleberry for testing!

 

[300_whisper]

Very cool. Thanks for sharing. Not sure if I saw this mentioned yet, but will this design impact case capacity? Will the tail cause any kind of compression issues?

I’m all for new and creative ideas. Again, very cool.

 

[Ballisticboy]

You need to measure flight drag coefficients for a true comparison of drag. I have seen very low drag designs which in use give a higher drag coefficient due to yaw induced drag. In testing and tracking different bullets using full size radars, I have seen conventional bullets with drag coefficients fairly close to 0.24 at Mach 2.5. We would use a minimum of 30 tracked bullets of each kind, fired 10 in each serial on three different occasions, to produce the Cd/Mach number drag curves. Unfortunately, fixed head radars will not be suitable except for obtaining muzzle velocities, making testing extremely expensive.

Dynamic stability could be a problem with designs such as yours. The boat tail angle will be critical, it looks a little high to me. The issue with very long boat tails is that the point where the air breaks away from the tail may vary with yaw angle, which will cause the dynamic problems. The ratio between the moments of inertia will also not be favourable.

However, don't let all the above put you off, there is still room for changing bullet designs and trying different things. I have seen designs similar to these before. In each case, the stability has been the deciding factor, in particular the dynamic stability, which is extremely difficult to accurately predict.

 

[300_whisper]

Anymore updates on this? @HappyHellfire

 

[Coyotefurharvester]

Copyrights and patents immediately.

 

[HappyHellfire]

I finally got it all working. It has been a long road. Check out my online store at AerospikeBullets.com