Re: Best known BC, any caliber
I dont want to turn this interesting topic into yes/no argument. I have no experience shooting tubular bullets whatsoever. Also, I dont meant to question your knowledge with bigger sabot/tube projectiles. English is my third language, just want to clear out these points. Sometimes my translation result is curious or even rude, unintentionally.
I still have feeling that we are partly talking about different things. You talk about bigger guns, Im talking about .30 cal / 5-8mm projectiles.
Firstly, when I mentioned saboted ammunition accuracy problems, I mean small rifle calibers "Under .50cal" ,as I said.
Only smaller sabot system in military use I´m aware of is is Swedish PSG90 -sniper rifle ammo, and its problem is inaccuracy too. But idea is to compensate it with smaller drop when exact range is not known or there is no time to define it.
So if there is a working sabot system for small rifle calibers nowdays , I haven´t heard about it. Feel free to share manufacturer/model if you know one.
What comes to that old design and drive bands, original text mentions that copper drive band was used in early designs with steel projectile, but later version (as in pic) did not need it since sabot was touching and did same thing.
And I would not laugh to shape too much either. They did not have fancy computers, but still managed to get shape right:
This is Sears-Haack shape from 1947, which (still) produces lowest theoretical wave drag in supersonic area.
If you compare it to tubular bullet silhouette designed about 60 years earlyer- by the men who "<span style="font-style: italic">had no idea of what they were doing with respect to supersonic flows</span>", as you described their knowledge. They weren't too far IMO. Gotta respect old trial-error method.
Tubular bullet needs always sabot, as it did hundred years ago.
I have no access to big manufacturers R&D departments or military applications- but small caliber sabots aren't working at the moment. As they didn't 100 years ago. Latest commercial trial and failure was done by Winchester in late 90´s or so- "Accelerator" was name of sabot cartridge if I recall correctly. And same inaccuracy was still a problem.
What comes to tubes in SMALL bullets and supersonic airspeed- I know that modernized version of that design has been simulated with high-end design softwares year-two ago. Results were, modestly said, very promising. Guy who did it is a member of SH, but I wont tell any details of that test. He may tell it if he wants.
<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: groper</div><div class="ubbcode-body"><div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: JL</div><div class="ubbcode-body">
All saboted bullets are still suffering exactly same problems than 100 years ago. Poor accuracy. Constant sabot separation is virtually impossible to achieve with tiny scale parts.
50cals and up are different story.
Another problem would be wind drift, even if sabot problem would be solved. But this topic was all about high BC itself, thought why not to mention about old idea.
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Not true, there was nothing wrong with the accuracy of the MODERN tubular projectiles, in fact they were more accurate than conventional projectiles. As i said, the problem lies within the limited range. The concept was abandoned in favour of the kinetic energy on target, terminal performance and payload potential of a conventional projectile with respect to the intended targets (being aircraft).
That old design you depicted, they had no idea of what they were doing with respect to supersonic flows and wave drag back in those days. The internal and external angles were not optimized and had no chance of getting it right with their limited knowledge not to mention the drive bands, sabot and obturation integration.
The modern tubular projectile has a drag coefficent about half what a normal VLD projectile has until about mach 1.8 when it all goes bad REAL QUICK thereafter. </div></div>