Comically Absurd Rifles & Bullets

[perttime]

Difficult.

Why?

You need to get several things working in balance, to get speed out of bullets: bullet weight, barrel length, rifling twist, burning rates, amount of powder, pressure (enough but not too much), strength of the case, strength of barrel and action.

So, let's discuss the simplest part of the equation: Bullet weight, burning rates, and powder quantity...

Bullet weight:
up to some point, it is easier to accelerate a light bullet to high speed, but light bullets have disadvantages in in-flight performance and power delivered to the target. Sabot projectiles may help with in-flight performance.
Burning rates and powder quantity:
Ideally, you'd have your powder produce as much pressure as your components can take safely, for as long as the bullet is in the barrel.
If you use fast burning powder, you get high initial pressure but it falls off rapidly. With some lower powered cartridges like .22LR and your normal pistol cartridges, the bullet will actually start slowing down in a rifle size barrel. Use more of the fast powder, and you blow up your gun.
If you use slow powder, pressure builds up slowly and the bullet keeps accelerating for longer - if you have a long barrel. At some point, the pressure will still fall off.
There's powders where the granules are shaped to provide a progressive burning rate, but there's only so much you can accomplish with this.
If you manage to get a combination of bullet and powder (chemistry and granule shape), that maintains high pressure for a long time without blowing up the gun - you still need a barrel that is long enough to contain the bullet while the pressure is up. If we are talking about man-portable rifles, there's limits to how long you want to go.

You could go for a bullet that becomes a rocket after it leaves the barrel. I don't know much about rocket performance, but think that additional complications come into play there.

Lots of powder and high velocities wear out a barrel quickly. For a pretty regular rifle at 3000 fps, 3000 rounds is normal ACCURATE life for a barrel. Some start losing accuracy at around 1500 rounds, some may go to 5000. Add more speed and you are soon in hundreds of rounds of accurate barrel life.
http://www.accurateshooter.com/technical-articles/facts-about-barrel-life/

[PR19_Kit]

PR19_Kit

You sound like you hunted a lot as well

No I didn't, but I did a LOT of target shooting and owned two of my own weapons.

[pyro-manic]

pyro-manic
3. Yeah, I've heard of a guided sniper-round: Smart-bomb merges with rifle-bullet -- I guess it was only a matter of time.
4. As for the gas-gun idea: I would assume the rupture disc would be permanently destroyed after every shot...

Yes. You'd have to replenish the hydrogen too. Not really practical as a weapon. Maybe a cluster of pre-primed chambers like a revolver cannon could be workable. Still tricky, though.

The smart bullets are .50BMG and laser-guided - there's footage on youtube. Search for DARPA EXACTO.

[sandiego89]

I imagine the Davy Crockett nuclear device would count as a comically absurd rifle and bullet....

It was a smoothbore, recoiless rifle, with a very interesting "bullet"

[KJ_Lesnick]

perttime

Bullet weight: up to some point, it is easier to accelerate a light bullet to high speed

One reason the 5.56 x 45 has such a high muzzle velocity compared to the 7.62 x 51...

but light bullets have disadvantages in in-flight performance

More easily nudged along by wind...

and power delivered to the target.

Yup F=MA, might be more A, but less M.

Burning rates and powder quantity: Ideally, you'd have your powder produce as much pressure as your components can take safely, for as long as the bullet is in the barrel.

Yup

If you use fast burning powder, you get high initial pressure but it falls off rapidly. With some lower powered cartridges like .22LR and your normal pistol cartridges, the bullet will actually start slowing down in a rifle size barrel. Use more of the fast powder, and you blow up your gun.

Well, that depends on the barrel strength.  There have been gun concepts like "metal storm" that actually rely on superposed bullets (I'm not sure if they're arranged in the traditional casing/bullet configuration or merely a bullet with powder in the back) -- regardless, several rounds going off one behind the other produces very high pressure in the barrel.

If you use slow powder, pressure builds up slowly and the bullet keeps accelerating for longer - if you have a long barrel. At some point, the pressure will still fall off.

So long as the bullet keeps accelerating until it leaves the barrel... and without having to deal with excessive pressures the barrel doesn't have to be built to ridiculous standards.

There's powders where the granules are shaped to provide a progressive burning rate, but there's only so much you can accomplish with this.

How about using some kind of solid-rocket fuel?  Gunpowder were used in primitive rockets, and I've built and fired a few using a propellent that was more or less gunpowder.  Well, the space-shuttle uses aluminum or aluminum oxide and ammonium perchlorate bound in something that gives a rubber like texture.

This might be a little excessive (ammonium perchlorate burns at something like 8,000 degrees)... but you could get something that produces more heat and pressure than gunpowder though.

you still need a barrel that is long enough to contain the bullet while the pressure is up. If we are talking about man-portable rifles, there's limits to how long you want to go.

Yup... there are ideas which could involve relief valves.

You could go for a bullet that becomes a rocket after it leaves the barrel. I don't know much about rocket performance, but think that additional complications come into play there.

True enough, plus after awhile you're talking about a rocket.

Lots of powder and high velocities wear out a barrel quickly.

Yup

On a different subject: I remember a concept that involved producing a vacuum in front of the gun: The idea is it'd reduce resistance and accelerate the expansion of the gases (less resistance on one side)


pyro-manic

Yes.

Is there anything that could work like a rupture disc that won't be ruined every time you fire a round?

You'd have to replenish the hydrogen too.

True

Not really practical as a weapon. Maybe a cluster of pre-primed chambers like a revolver cannon could be workable. Still tricky, though.

True enough and by that point why not just build a railgun... now that's some speed.



Sandiego89

Davy Crocket didn't have rifling, but I'll list it anyway

Also... However this http://en.wikipedia.org/wiki/M65_Atomic_Cannon

[pyro-manic]

Some ridiculously over-built valve system, perhaps. But I don't know much about how feasible (never mind practical) that would be. Probably very bulky.

[Rheged]

Is this a place or time to introduce into the discussion the V3 weapon (‎Mimoyecques , France),  the late Saddam Hussein's Mother of all Guns (barrel sections forged in Sheffield) and/ or the Peenemunde Arrow   shell?........or even Project Harp??    You probably all know all about these, but there's a few seconds worth   of research below as an aide memoire.

http://en.wikipedia.org/wiki/V-3_cannon

http://www.nytimes.com/1992/10/28/us/exports-by-us-aided-iraq-super-gun-house-banking-chief-says.html

http://www.warandtactics.com/smf/experimental-prototypes-research-in-the-reich/peenemunde-arrow-shells/



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

[perttime]

Some ridiculously over-built valve system, perhaps. But I don't know much about how feasible (never mind practical) that would be. Probably very bulky.

If you mean valves that open or close while the bullets is accelerating in the barrel, you also need the valves to work quickly and pretty well timed:
"So how long does a centerfire bullet (with 3000 fps MV) typically stay in the bore? The answer is about .002 seconds."
http://www.accurateshooter.com/technical-articles/facts-about-barrel-life/

[NARSES2]

the late Saddam Hussein's Mother of all Guns (barrel sections forged in Sheffield)

Allegedly ! I knew the people involved and they all swore blind they were for an oil refinery. They were subject to some quite severe questioning by the police and were under arrest at the time. Strangely another forging company in the West Midlands who were allegedly working on the same kit were not spoken to at all. This companies parts could in no way be deemed to be connected with the oil industry.

My personal view was that at least one of the companies involved had been duped.

[KJ_Lesnick]

PR19_Kit

No I didn't, but I did a LOT of target shooting

Oh, cool.

owned two of my own weapons.

May I ask what kind?


Rheged

Is this a place or time to introduce into the discussion the V3 weapon (‎Mimoyecques , France),  the late Saddam Hussein's Mother of all Guns (barrel sections forged in Sheffield) and/ or the Peenemunde Arrow   shell?........or even Project Harp??    You probably all know all about these, but there's a few seconds worth   of research below as an aide memoire.

The Peenemunde arrow was definitely an interesting design, and the V-3 was a pretty creative idea though it has one major problem (it depends on multiple charges)



perttime

If you mean valves that open or close while the bullets is accelerating in the barrel, you also need the valves to work quickly and pretty well timed: "So how long does a centerfire bullet (with 3000 fps MV) typically stay in the bore? The answer is about .002 seconds."

Good point... camera shutters open and close real fast 1/1000 or 1/2000 of a second (0.001 to 0.0005), which would theoretically allow a 6,000 to 12,000 f/s bullet.

[PR19_Kit]

owned two of my own weapons.

May I ask what kind?

One was a BSA Martini International Mk1 and the other was a Walther KKM, both in .22LR of course. I carved my own thumb-hole stock for the BSA, not very well, but it was more comfortable on the range.

[KJ_Lesnick]

PR19_Kit

Did you fire at a stationary target or at clay pigeons?

[rickshaw]

PR19_Kit

Did you fire at a stationary target or at clay pigeons?

Kendra/Robyn, PR10_Kit mentioned the calibres of his firearms.  Do you honestly believe that a .22 LR calibre weapon would be very capable of shooting clay pigeons effectively when you normally use shotguns for that sort of target?   

[PR19_Kit]

 

I used a Browning Sweet 16 for shooting clays, and was very much frowned upon for a] firing from the hip and b] using an auto anyway! 'Proper' shooters used over-unders at a pinch but really preferred to use side-by-sides in those sort of circles. 

Most of my target shooting was on paper targets at 25 yards, both indoor and outdoors, but I did use both weapons at 200 yards at Bisley a few times. The round was flying so slowly by the time it got there I almost had enough time to swap to the spotting scope and watch it hit! 22LR at that range needed a massive amount of elevation too, I found it most uncomfortable.

[KJ_Lesnick]

Rickshaw,

Sorry, it was an attempt at humor.  I don't know why -- it wasn't terribly funny