Whats The Advantage of a Boat Tail Projectile?

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There's ample data that boat tails are more aerodynamic, especially as the caliber increases. By the time you get to artillery, the difference is notable.

Anyone with a set of swaging dies and a Labradar can prove it to themselves in an afternoon. We can argue about WHY boat tails are more aerodynamic, but there's no question that they are. This was known as far back as the Lebel.
 
Steelangel said:
View attachment 797014
This is a Skunk Works Laboratory image of the shockwave parting the airflow. There is nothing but reverberation behind the tip of the bullet. It's actually in a vacuum of space behind the initial shock wave. Where there's no air, there's no airflow. Thanks for supplying the image...
Edited for Skunk Works Labs Ref - https://www.lockheedmartin.com/en-us/who-we-are/business-areas/aeronautics/skunkworks.html
Click to expand...
The word 'vacuum' is a relative term....meaning 'lower pressure' in this case. There is no such thing as a total vacuum which would be void of any and all molecules and that's not possible. Even out in deep space there are bits of things floating around....VERY far apart and in low density, but still present.
If there actually was a vacuum behind the tip of the bullet....no shock waves would be able to be formed, but many are clearly visible in the photo. This is because behind the primary shock front is a region of lower pressure but certainly not a total vacuum so shapes can and do create additional shock waves. Notice the cannelure creating one as well as the beginning of the tail taper....all play a part and add drag.
Many target bullets will be flat based and this is because that's an easier thing to build precisely than a boat tail. This precision is needed for a clean and consistent emergence from the muzzle which is much more important to target accuracy than any aerodynamic benefit the boat tail can offer...which it does. Only at long range where drop and wind deflection begin to play a larger part in hitting ones target do the benefits of boat tails start to overwhelm the slight imprecision they can show at close range due to their leaving the muzzle with a bit more variables.
 
While a significant portion of those that post on gun boards see themselves as the end all, be all, know all of firearms knowledge and information, I’ll defer to the manufacturers of high end target bullets. They do it for a living, and their engineers have a lot more info on this subject than most anyone here.

Since their business is super competitive (both in matches and in business terms), and they mostly or all use boat tails on their long range match bullets, I’m going with boat tail for the win (pretty cool pun, huh?). :)

If you really think boat tails don’t help, go ahead and call Sierra, Berger, or Nosler and explain to them why they’re all wrong.
 
The trucking companies like them. I read an article that said gas consumption drops by 5% when a trailer has a tail on it. The article also went on to say that the tails also "....go a long way to increasing safety, stability and visibility,” (I'm assuming the visibility part is that cars can't get as close to the back end of the trailer - so it's more likely a trailing car will be visible in the truck's mirrors.) Another article stated

The article stated the trailing low-pressure "drag" is smaller with the tail because the tail brings the air around the rear corners of the trailer before the low pressure is created.
 

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redneck2 said:
While a significant portion of those that post on gun boards see themselves as the end all, be all, know all of firearms knowledge and information, I’ll defer to the manufacturers of high end target bullets. They do it for a living, and their engineers have a lot more info on this subject than most anyone here.

Since their business is super competitive (both in matches and in business terms), and they mostly or all use boat tails on their long range match bullets, I’m going with boat tail for the win (pretty cool pun, huh?). :)

If you really think boat tails don’t help, go ahead and call Sierra, Berger, or Nosler and explain to them why they’re all wrong.
Click to expand...

Don't believe I said they don't help in some ways, only not in the aerodynamic realm. And I've worked with many company 'Enginerds' ... PLEASE spare me the grief today! :confused: Thanx!..
 
Flat base - flat earth?

Is there a connection?

Seriously though, we get marketed to a lot by bullet manufacturers but I’d be quicker to question the merits of ballistic tips before I’d call the boat tail just a bunch of hype.
 
Nature Boy said:
Flat base - flat earth?

Is there a connection?

Seriously though, we get marketed to a lot by bullet manufacturers but I’d be quicker to question the merits of ballistic tips before I’d call the boat tail just a bunch of hype.
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Ballistic tips work too, especially the Hornady ones that don't melt in flight. All else being equal a longer bullet of the same weight has a higher BC. This has been confirmed repeatedly by dopler radar and drop measurement. Voids in the nose like Lapua uses on the Scenar line work for the same reason.
 
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Steelangel said:
Do you document your 'dope chart' in all directions? Very entertaining video for ya!..
Click to expand...


I didn't watch your video until now. Now that I see that you believe the earth is flat it also makes sense how you think a bullet or airplane flies through a vacuum. Good day and good luck with your mental illness.
 
CapnMac said:
Isn't there an internal ballistics effect with boattails and the way the propellant gasses address the end of the bullet?
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Flat Base vs Boat Tail bullets.

Flat Base - are more accurate when supersonic.

Boat Tail - are more accurate and efficient subsonic.

The Supersonic pressure wave negates any drag effect from the tail of a standard bullet. Boat tails are generally used to aid in production bullet seating.

What affects accuracy is how the bullet leaves the muzzle, and how the gasses (muzzle blast) affect it.

When a Flat Base bullets leaves the muzzle, it leaves immediately and cleanly. Gasses are directed out from the flat base perpendicular and away.

With a Boat Tail, the tail is still in the bore when the gasses are unsealed. The barrel is also vibrating, so the bore/bullet gap is also variable. These variable gasses are directed parallel, and then deflected off the tapered tail, imparting uneven perpendicular forces on the tail of the bullet while the tail is still in the bore, and as it exits.

Not an inherently good condition for precision.

When the bullets go transonic, the boat tail becomes much more efficient.

VLD bullet design may have improved supersonic ballistic coefficients, but they have not resolved the issue of bullet egress.




GR
 
Glad to see a new member on THR. I see you just joined yesterday. We are a pretty laid back group here, and we all love to gain knowledge. Try putting on the brakes a little and gain some credibility before telling us all how wrong we are. You may be totally right, but no one here listens to the know it alls. We welcome everyone and all the knowledge they bring along but we are not AR15.com. Just sayin.
 
Garandimal said:
[...]
The Supersonic pressure wave negates any drag effect from the tail of a standard bullet. Boat tails are generally used to aid in production bullet seating.
[...]
GR
Click to expand...

I don't remember learning anything about supersonic waves negating drag effects. My understanding is in supersonic flight the region "inside" the supersonic region has drastic affects on fluid characteristics but that it was absolutely still a fluid. Thus you would still have drag effects.

However, it's been said multiple times in the thread that counters what I've learned. Does anyone have any literature to support the supersonic pressure wave negating drag?
 
Steelangel said:
Don't believe I said they don't help in some ways, only not in the aerodynamic realm.
Click to expand...

Rogue909 said:
...you would still have drag effects.

However, it's been said multiple times in the thread that counters what I've learned. Does anyone have any literature to support the supersonic pressure wave negating drag?
Click to expand...


At supersonic speeds, there is still an aerodynamic drag. The drag is from the compressed shock wave rather than the viscous fluid flow, but it is still within the realm of aerodynamics. In post #25, I explained how the boat-tail addresses a critical aspect known about wave drag in supersonic aerodynamics.
 
Rogue909 said:
I don't remember learning anything about supersonic waves negating drag effects. My understanding is in supersonic flight the region "inside" the supersonic region has drastic affects on fluid characteristics but that it was absolutely still a fluid. Thus you would still have drag effects.

However, it's been said multiple times in the thread that counters what I've learned. Does anyone have any literature to support the supersonic pressure wave negating drag?
Click to expand...

At supersonic speeds, there is no laminar flow for the boat-tail to take advantage of. It's just the end of the bullet in the wake inside the pressure cone.




GR
 
ontarget said:
Glad to see a new member on THR. I see you just joined yesterday. We are a pretty laid back group here, and we all love to gain knowledge. Try putting on the brakes a little and gain some credibility before telling us all how wrong we are. You may be totally right, but no one here listens to the know it alls. We welcome everyone and all the knowledge they bring along but we are not AR15.com. Just sayin.
Click to expand...
Looked pretty sleepy around here, I wanted to shake you guys up a bit, lolol.. :rofl: And Thanks for the warm welcome!
 
denton said:
Not much. Boattail and flat base both get the same acceleration from the same amount of pressure.
Click to expand...
one would think that given the same weight, the shank contacting the barrel would be significantly shorter, meaning less friction.
 
Steelangel said:
Don't believe I said they don't help in some ways, only not in the aerodynamic realm. And I've worked with many company 'Enginerds' ... PLEASE spare me the grief today! :confused: Thanx!..
Click to expand...
No, you started it. Don't dish it out if you can't take it. Not a very High Road way to join the forum. Robert should have locked this when he threatened to.
 
Garandimal said:
At supersonic speeds, there is no laminar flow for the boat-tail to take advantage of. It's just the end of the bullet in the wake inside the pressure cone.
GR
Click to expand...

The boat tail does not need laminar flow to work because there is not just one pressure cone.

Bullet-Spark-Shadowgraph.jpg


Notice multiple shock waves off the bullet at M1.3. You see them here also with a different object:

airbos_f7_p5.jpg

The idea that a supersonic object is only acted on by the drag of a single shock wave is invalid.
 
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