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Military Guns and Ammunition

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tubular bullets   General Military Discussion

Started 7-Jan by smg762; 2508 views.
Red7272

From: Red7272

10-Jan

autogun said:

No, the pale grey ring is a driving band of groove diameter so it provides obturation and takes the rifling. The shell body immediately above the driving band is of bore diameter, so the shell is supported in the barrel in two places.

A solid copper investment casting might make an interesting VLD projectile with just the boat tail and ogive and no actual cylindrical part to the projectile beyond 2 or 3 mm for gas tightness. 

Mr. T (MrT4)

From: Mr. T (MrT4)

10-Jan

Would that not result in a rather picky bullet hard to make shoot well?

Red7272

From: Red7272

10-Jan

Mr. T (MrT4) said:

Would that not result in a rather picky bullet hard to make shoot well?

I don't think so. Investment casting is fairly cheap and the accuracy would be at least as good as conventional lead cored bullet manufacture. Might even be possible to stamp them but the angled fins could be an issue. 

Edit. Opps no misplaced a decimal point. Maybe stamping would work but it might not be practical. 

  • Edited 10 January 2021 21:01  by  Red7272
smg762

From: smg762

11-Jan

In layman's terms what would this projo look like..... A VLD bullet with an extremely short bearing surface? 

By 'angles fins ' are you referring to my striations idea or something else? 

I was thinking if you had a pusher wad behind bullets,  it might allow all sorts of previously-impossible shapes (e.g..  fins).  And no loss of accuracy. 

Perhaps instead of striations,  you could have a very short bearing surface with fins that are actually designed to ride the bore? 

  • Edited 11 January 2021 11:47  by  smg762
dobrodan

From: dobrodan

11-Jan

If you first are going to make a tubular bullet, then maybe it could be worthwhile to see if a solid-fuel ram-jet could be integrated in the design.

Not necessarily for extra acceleration, but perhaps being able to reduce the drag, due to the base-bleed principle, like tracers, but much more effective.

  • Edited 11 January 2021 15:06  by  dobrodan
Red7272

From: Red7272

11-Jan

dobrodan said:

Not necessarily for extra acceleration, but perhaps being able to reduce the drag, due to the base-bleed principle, like tracers, but much more effective.

Yup, full tracer/base bleed would work. The 5.45 is 50 years old. A better shaped tracer round with an AP tip and base bleed would do everything he wants out to 600 metres. Ramjet projectiles in rifle calibres are problematic I suspect. 

smg762

From: smg762

12-Jan

I was leaning more to the idea of fins that ride the bore (combined with pusher wad)

the fins would be less sharp,  more resembling the soft shaped fins on Tonys pic. 

The benefit is not so Much from the fins themselves.... instead,  you get more swept volume,  basically a sabot effect... allowing a. 17 or. 18 cal,  with 556 energies. 

Yet another idea that,  if it worked,  would be great

Moving (very briefly) back to sabot,  I thought of a cup type sabot which is extremely thin-walled.  This means the projo is almost touching the bore. Your 5mm bullet in a 5.7mm bore.

  It could eliminate in-bore yawing.... keeps bullet concentric....

Either of these sound reasonable? 

  • Edited 12 January 2021 0:37  by  smg762
dobrodan

From: dobrodan

12-Jan

In a normal tracer, the pyro-technic fuel is placed in the bottom, and will burn in a relatively low-pressure-evironment in the slipstream of the projectile.

In a tubular projectile, the tracer-fuel could be placed on the inside of the tube, either behind a restriction that wil compress the air, or possibly by the material itself being the restriction.

By the tip of the projectile being open, a windpressure of almost 4.8ATM will be created at 900m/s, which will make a PO2 of 1.008, which is very close  to that of 100% O2 at atmospheric pressure.

Which again will make other andmore energy-rich pyro-technical fuels possible.

The point here is not necessarily to accellerate the projectile, but "supercharge" the tracer-fuel, to make it produce more exhaust, which will give it a certain thrust, so that it can help the projectile maintain a higher velocity, and a flatter trajectory.

The way a ramjet works, is by basically taking a certain area of air (equal to the frontal area of the air-intake,) at a given pressure.

 Compress it with a flow-restriction that slow the air to subsonic velocity.

 Add fuel

 Combust the air/fuel mix in a conical combustion-chamber/nozzle which has a larger area than the restriction. 

The exhaust-gas is ejected out the nozzle, at a higher mass, volume and velocity than the intake-air, at a higher pressure than at the intake, but lower than in the flow-restriction.

Which should equal to thrust.



 

  • Edited 12 January 2021 9:56  by  dobrodan
Red7272

From: Red7272

12-Jan

Now package all that into a 7 mm projectile for less than $0.4.

dobrodan

From: dobrodan

12-Jan

Why 7mm?

Why not 10mm?

Or 12,7mm?

If you are going to make a tubular projectile, with a ram-jet-tracer, the diameter of the projectile does not need to be as small as possible any longer. It would have some of the same characteristics as a saboted projectile, which requires a large swept area, with a relatively low projectile weight, to aquire a fast muzzle-velocity...

And why should it be very expensive? You cut a tube into the correct length, and squeeze it into a mould, giving it the preferred shape, and insert a ring of the fuel of choice... And then seal it with something that can ignite the fuel and dissolve almost instantly, and load it into a propellant fille cartridge.

Yes, figuring out how to do it would probably cost a bit, but manufacturing it would probably be quite affordable

  • Edited 12 January 2021 14:41  by  dobrodan
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