Man-Portable Light Gas Gun?

[atek3]

They've been referenced in several threads on there on speculative future weapons, but I don't think many people have done serious investigation into their feasibility.

The basic idea is that you use'd use charge of gun powder which drives a 40mm nylon piston down a long tube containing compressed hydrogen. The Compressed hydrogen gets REALLY compressed, breaking a pressure disk, the hydrogen travels through a high-pressure coupler into an evacuated 50 caliber barrel containing an APFSDS projectile. Velocities from 10-20,000 fps are possible.

Containing the chamber pressures would likely be challenging in a lightweight platform, however weight would be a good thing as such a rifle would have between 3-25 times the recoil of a 50 BMG rifle. Also, reloading speed would be slow. benEzra proposed using a self contained, disposable piston idea, which I think might work, but given the pressures and temperatures we're talking I wouldn't be surprised if the case was explosively welded to the 'chamber'.

Near as I can tell, given current technology levels and the NFA prohibition on destructive devices this is would probably be the most powerful NFA firearm in existence. (I don't count 4-bores because their status as 'sporting' could be revoked instantly)

atek3

 

[Justin]

If such a design requires the use of a rifled barrel, you're going to have to replace barrels on nearly a constant basis.

Many high velocity cartridges need to have the barrels replaced every 2,000-4,000 rounds, and their velocities aren't even half of what you're proposing.

 

[LoneCoon]

What about rifling the projectile itself?

 

[atek3]

APFSDS... the FS stands for fin stabilized... the gun would definitely be smoothbore.

High-pressure, high-temperature hydrogen would probably embrittle the barrel steel. They might be rated for only a few shots.

I'm not touching on the economic feasibility, just the technical feasibility.

 

[Justin]

*smacks forehead*

Plainly I need more coffee.

 

[everallm]

Atek

Your mixing your numbers a little

The modified 40 mm cannon that NASA uses ejects a 5mm not a 50 caliber projectile to get the velocities your discussing.

A 50 caliber tube has a surface area roughly 6.5 x greater than that of the 5mm so velocity would be dramatically lower,

 

[RevolvingGarbage]

Atek

Your mixing your numbers a little

The modified 40 mm cannon that NASA uses ejects a 5mm not a 50 caliber projectile to get the velocities your discussing.

A 50 caliber tube has a surface area roughly 6.5 x greater than that of the 5mm so velocity would be dramatically lower,

Woah, what?

What is NASA using this for?

 

[atek3]

The Range G gun gets roughly 15,000 fps velocities from a 14 inch piston and an 8 inch bore. That gives us roughly 3x difference in surface area. For a 50 cal barrel, the corresponding piston size would be .875 in. Using a 40mm barrel would give a ratio of 9.9x, a comfortable safety margin. I think the relatively low velocity from the NASA Gun results from using a heavy for caliber projectile and a very short one meter barrel.

When I say "man-portable", I'm not talking 'replace the remington 700', or even 'replace the Barrett', I'm talking 'replace the Tankbüchse 41 or Lahti'

 

[everallm]

Google am your friend....

http://en.wikipedia.org/wiki/Light_gas_gun

 

[atek3]

duh, that's where I got the fundamental information for my posts. And you?

 

[CYANIDEGENOCIDE]

nasa uses these to test space craft against asteroid impact, not all asteroids are moon sized, most are small like pebbles. really the asteroids can travel much faster than what a LGG is capable of producing but tis the best we have

 

[Snowdog]

atek3, I think everallm was suggesting the link to RevolvingGarbage.

 

[atek3]

Hah... in that case, I apologize everallm...

this is why @reply is so handy

 

[Rembrandt]

Mildly reminiscent of a tater shoot'n spud gun.....