Bullet Surface Texture

[Popsbengo]

I'm aware of certain textured surfaces being useful in reducing drag - being used for both hydrodynamic and aerodynamic performance enhancements

I was wondering if anyone has done any research on effects of bullet surface texture on external ballistic performance?  For example, brushed micro grooves vs. highly polished

Of course, bullets are spinning at around 200,000rpm and travelling supersonically for most applications so it may be wholly irrelevant.

Thoughts 🤫

[Nick 53]

Hi is why bullets purchased are so shiny? To assist in flight less drag I assume. 

Thanks nick 

[DaveT]

By the time it's been bashed into the rifling I would think that surface finish would not matter.

[gazzarM1]

Us shooters luv shiny stuff....

[meles meles]

You might like to research the topic of artillery shells which ride up the barrel on driving bands that obturate the propellant gases and reduce friction whilst isolating the shell itself from contact with the bore. The barrel experiences less wear and the shell itself can have a textured surface. Knowingly or not, the taxpayers of many nations have spent a lot of money on the technologies involved...

[ejg223]

I asked that or similar question Brian Lutz a year or two ago. I was asking if there would be any aerodynamic advantage to use polygon barrels because of the smoother bullet surface after leaving the barrel. He answered "very little".

edi 

[ezmobile]

15 hours ago, meles meles said:

You might like to research the topic of artillery shells which ride up the barrel on driving bands that obturate the propellant gases and reduce friction whilst isolating the shell itself from contact with the bore. The barrel experiences less wear and the shell itself can have a textured surface. Knowingly or not, the taxpayers of many nations have spent a lot of money on the technologies involved...

Is it not the case that while "driving bands" are made of a soft metal, like copper or similar, the shell casing itself is much harder - steel perhaps, thereby containing the bursting charge to a higher pressure, and also steel on steel would wreck the barrel rifling after a few rounds.

I'm not an expert on this, just working with common sense. 

[ezmobile]

17 hours ago, Nick 53 said:

Hi is why bullets purchased are so shiny? To assist in flight less drag I assume. 

Thanks nick 

My thought would be that nearly all copper objects machined are shiny (just think of copper plumbing tubes & fittings, copper wire etc.) because (a) they're newly made. (b) they are boxed immediately after production, helping to prevent oxidisation on the material. I rather doubt that they're actually "polished".

[Nick 53]

Well my copper bullets get molly coated so a different shine!!

Nick 

[Ballistol]

The driving band indeed helps with obturation, but it forcibly contacts the rifling of the barrel forming the only point of physical contact to the barrel itself. The rifling effectively engraves the band as it is driven up the barrel thereby imparting the spin necessary to stabilise the shell. 
The driving band is machined to very precise tolerances and is consequently bright when machined, but this quickly oxidises and is of no consequence to the end user.

[Popsbengo]

not really interested in shells here, my OP was about surface texture of small arms bullets contributing (or not) to aerodynamic performance.

Side issues are very interesting but they do drag the focus away from the original

[ezmobile]

5 hours ago, Ballistol said:

The driving band indeed helps with obturation, but it forcibly contacts the rifling of the barrel forming the only point of physical contact to the barrel itself. The rifling effectively engraves the band as it is driven up the barrel thereby imparting the spin necessary to stabilise the shell. 
The driving band is machined to very precise tolerances and is consequently bright when machined, but this quickly oxidises and is of no consequence to the end user.

Couldn't have explained it better myself!

As for surface texture, my guess would be that its the actual shape of the bullet that the biggest contributor to aerodynamic performance. Wouldn't putting a texture on the surface, as opposed to a smooth finish,  just impair it? That said, I've heard that the dimples in a golf ball apparently aid in its flight.  

[Brillo]

In my experience and in practice I’ve not found it to make any difference up to 1000 yards.

I had a batch of bullets that corrosion on the tips so I dry tumbled them. These came out a dull finish compared to the usual shiny. The POI was no different to the shiny batch.

[meles meles]

On 2/11/2020 at 10:44 AM, Popsbengo said:

not really interested in shells here, my OP was about surface texture of small arms bullets contributing (or not) to aerodynamic performance.

Side issues are very interesting but they do drag the focus away from the original

Indeed so, but we understand that clever oomans, with their big brains and stereoscopic vision,  can apply pertinent knowledge gained in one area to a second field of endeavour. 

 

 

* Wanders off to look at the small, solid projectile with nylon driving bands in the display case at the far side of the lab *

[Popsbengo]

pertinent knowledge !

if only...

 

[meles meles]

Our opinion is worth exactly what you paid for it 😉

[Popsbengo]

2 minutes ago, meles meles said:

Our opinion is worth exactly what you paid for it 😉

I was making a general plea  - badger input is always welcome even if you have no pockets for coins