12Ga Tubular Bullet

[Tubular]

This concept is aimed at ultra long range target shooting (Ko2M and similar) where reducing wind effects by minimizing time of flight is important. This design aims to reduce time of flight by increasing muzzle velocity, maintaining that velocity downrange by maximizing the ballistic coefficient, and by having a very flat trajectory.

1. The bullet is a tubular design with a pusher (See the drawing below.) and is based on a 12Ga bore. The bullet weight is 300gr in tungsten and the pusher is 17.75gr in Nylon (PA).

2. A 1750m/s muzzle velocity is the target and the 12Ga bore should allow for the increased force necessary to achieve it. The 12Ga bore gives a 4.5X increase in cross-sectional area vs. the 338 Lapua Magnum and 2.1X vs. the 50 BMG. At a 60,000 psi chamber-pressure the force acting on the tubular bullet would be 24,354 lbf, compared to the 338 Lapua Mag at 5,384 lbf and the 50 BMG at 11,781 lbf.

3. The reduced aerodynamic drag of the tubular design at elevated velocities will help reduce time of flight. At 700m/s the 12Ga tubular bullet has a Cd of ~0.1698. At 700m/s A 300gr 338 Lapua Magnum ‘Scenar’ bullet has a Cd of 0.2848, 68% greater. I didn’t find equivalent 50 BMG info (Velocity + bullet selection…).

4. 12Ga Tubular Bullet Ballistic Coefficient Calcs:

• Cd @ 700m/s = 0.1698 (Determined via. CFD)
• W = 300gr
• Cal^2 = (0.104in^2)^2 = 0.0108in^4 (I used the cross-sectional area of the tubular bullet. 0.104in^2, instead of the full 12Ga bore area.)
• i1 = 0.1698/0.593 = 0.2863
• BC1/G = 13.86 = 300/(7000)(0.0108)(0.2863) = 300/ 21.64 = 13.86
• i7 = 0.1698/0.298 = 0.5699
• BC7 / G7 = 6.96 = 300/(7000)(0.0108)(0.5699) = 300/ 43.08 = (G7 = 0.368 @ 700m/s for the 338 Lapua Mag + 300gr Scenar Bullet. G7 = 0.451 for the 50 BMG + 750gr Hornady A-MAX, velocity unknown.)
• Plugging the G7 figure from above and a 1750m/s muzzle-velocity into a ballistics calculator gives the time of flight to 3,500 meters is ~2.1 seconds and the terminal velocity is ~1660m/s.

5. This tubular bullet design has the ability to generate lift, so it can operate outside of a strictly ballistic trajectory. Using the ability to ‘fly’ will allow for the flattest possible flight path, further reducing the time of flight. I don’t know how to determine/factor in this aspect.

I ran everything through CFD (The second image is a 2D run at 350m/s showing the transonic air velocity behaviour.) to get the Cd numbers (250m/s to 1750m/s. Please see the graph below.) I put quite a bit of time into finding and reading what I could on the tubular/ring bullet/projectile topic, but I am sure I missed plenty. I rolled everything I have (CAD, CFD, patent info, etc.) up and put it on G-Drive for anyone that's interested.

I look forward to hearing what folks think.

Regards,

Jon

 

[Hobo Hilton]

The Navy has been working on that design for quite a while.

https://www.usni.org/magazines/proceedings/1893/july/krnka-hebler-tubular-projectiles

 

[Taylorbok]

I'm interested to hear about this.
I'd like to know how it's propelled?
I'd have to guess with it being able to "create lift" the wind would greatly affect it's direction of travel.
I have to figure that BC number is calculated how well it would travel through the air forward but doesn't account for a full value wind, it's got a huge side profile????

 

[Tubular]

You, sir, have a gift for understatement. Yes, the idea of hollow bullets is old (I believe these are the first.), 1893/1894.

Some visuals to go with your post...

 

[Tubular]

I'm interested to hear about this.
I'd like to know how it's propelled?
I'd have to guess with it being able to "create lift" the wind would greatly affect it's direction of travel.
I have to figure that BC number is calculated how well it would travel through the air forward but doesn't account for a full value wind, it's got a huge side profile????

I didn't go all the way down the rabbit hole with the design (I really only focussed on the bullet.) so I can see where it could be confusing. The bullet and pusher would need to be loaded into a cartridge, in this case a 12Ga shotgun case, and then fired out of a rifled 12Ga shotgun. Hope that's enough to clear that up.

Gravity orients the bullet such that lift is always 'up'. Vague, I know, but true none the less.

Wind drift was more than I could figure out frankly. The common mantra is "heavier is better!", but the formulas don't ask for weight, or frontal area, etc. Larger profile area, common for all of the bullets I'm aware of, doesn't seem to be factored in, so I don't know the answer.

 

[gwood]

I didn't see this on your G-drive:

Defense Technical Information Center

apps.dtic.mil

 

[Tubular]

I didn't see this on your G-drive:

Defense Technical Information Center

apps.dtic.mil

Thanks for that gwood! 40+ pages of know-how I hadn't seen before... I'll update things accordingly.

 

[badassgunworks]

It will have issues

 

[Tubular]

I should have put this image up originally (Below). Looking at the SAMI drawings for the shot-shell/cartridge and the chamber there would need to be some tweaking to make everything work. Seems like shotgun slugs have a different sort of relationship to the barrel entry than a rifle does...

I also spent some time going through the document gwood linked me to. That document and the R.A.G. project are the only two places where I have seen the tubular form-factor discussed without 'range-limiting' being a factor. 'Lift' being discussed as a feature of the tubular form-factor is still limited to the R.A.G. concept (Flatau mentions it as an aside in his "Machine Gun Comments"). I re-read a bunch of the research and still don't know how the angle-of-attack gets set when a tubular bullet is fired. The RAG documentation has an explanation but it doesn't seem right to me so I'll keep looking.

Last up was some house-cleaning for the file-download folder: I had a duplicate research doc in there that I deleted. I found one I failed to upload before and added that. I also found a couple of new patents and added those as well.