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tubular bullets   General Military Discussion

Started 7-Jan by smg762; 2501 views.
In reply toRe: msg 4
autogun

From: autogun

8-Jan

I have no idea of the technicalities involved.

jc56au

From: jc56au

9-Jan

Probably similar to aerodynamics to jet intakes on supersonic aircraft (except there they are trying to get the airflow subsonic for fuel burning.

Heaps of stuff on this but the maths/arithmetic gets out of control pretty quickly also the manufacture - the inside of the duct is one of the more expensive parts of the aircraft with variable geometry to handle the speed range

smg762

From: smg762

9-Jan

On a completely random note Tony,  I was told by a Swede marksman that they managed to get MOA at 900m with their 762 SLAP.  Is that reasonably impressive? 

Also another Swede posted extremely detailed info on his SLAP performance here 

https://www.sniperforums.com/threads/408-cheytac.30/

he was basically singing its praises,  saying that for him it shoots better than regular ball. 

Their setup looks simplistic,  it's a very short-for-caliber bullet in a cup-shaped sabot. 

  • Edited 09 January 2021 12:45  by  smg762
In reply toRe: msg 7
JPeelen

From: JPeelen

9-Jan

To me, the thread you linked is not so much about dispersion, but about the significant advantages of a flat trajectory and a short time of flight at medium and long range. Errors in sight setting, holdoff (moving target) as well as crosswind have much less negative effect on the mean point of impact.  

The Swedish intention to outweigh a somewhat larger dispersion (sabot) by having the mean point of impact more often on the target (flatter trajectory, shorter time of flight)  seems to have worked for them. If they really achieved the dispersion improvements indicated -I am a little sceptical in this regard- the better for them.    

smg762

From: smg762

9-Jan

We already know the increased hit probability you get from sabot projos. 

My point was he was suggesting impressive core accuracy- MOA or under.  

This conflicts with other sources which said it could be up to 33% less accurate than normal 762. 

It also maybe suggests that bullets,  not flechettes,  are the way to go with sabots.  

renatohm

From: renatohm

9-Jan

Under some circumstances, yes, APDS / SLAP works better than APFSDS, in others it's the opposite.

Things must also be weighed regarding accuracy and costs - 33% worse accuracy may be worth it in some roles but not in others.

Last but not least, this debate belongs to another thread - this one is about tubular bullets, not saboted ones.

JPeelen

From: JPeelen

9-Jan

When Hebler and Krnka experimented with tubular projectiles about 130 years ago, the goal was to dramatically reduce air drag. It was believed, the inner cross section would be passed by the air undisturbed. 

They could not know the peculiarities of supersonic aerodynamics and the creation of shock waves inside the tube by its "mouth". The plan works only at very high Mach numbers. If velocity drops beyond a critical value (dependent on tube diameter and length), the tube flow becomes choked. Therefore, modern existing tubular bullets (like the one shown by Tony, or the defunct Rheinmetall LKL-projectile) are used for achieving an additional brake effect. They are training projectiles for shorter ranges, not enhanced ranges. 

Hopefully someone fit in aerodynamics on this forum can tell us the approximate Mach number at which a 5.56 mm tubular projectile would work as intended. I would not be surprised if it were useful only while it flies well above Mach 3.          

  • Edited 09 January 2021 14:41  by  JPeelen
smg762

From: smg762

9-Jan

Vaguely returning back to the original subject,  could you have a bullet with striations running longitudally along its length. (From tail to nose)

To get a visual idea,  Google bullet striations and look at the 9mm rounds.  Imagine that but Much deeper. 

They could either be straight,  or angled which would add spin to bullet. 

Then you have a wad behind the bullet. 

The idea is that it gives the drag profile of a tiny caliber bullet,  but the overall bore size is closer to. 22 - thus it gives no barrel wear. 

Also,  someone has a patent for a disk shaped bullet

https://patents.google.com/patent/US20140150319A1/en

Regarding jpeelens thoughts on the tank training ammo being short ranged,   a rifles tubular ammo would only need be stable at 600m

  • Edited 09 January 2021 15:46  by  smg762
renatohm

From: renatohm

9-Jan

Aerodynamics is such a fascinating subject!

If useful only above a high Mach number, tubular projos could find a new life through rail guns, whose velocities are usually very high.

smg762

From: smg762

9-Jan

Does anyone have any thoughts on my striations idea?  Assuming it's viable I think it's far superior to tubular/sabots or anything else. 

Remember the idea is to emulate the drag profile of a microcaliber,  and yet avoid the barrel wear problems

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