Design an air rifle for the military

[bennedose]

Ok folks let me post a few back of envelope calculations - adopting some data from Timmy's post above and making a few assumptions. I will not post all the detailed math/conversions but just my assumptions and conclusions.

My reading tells me that the biggest energy/power barrier is taking a pellet above the speed of sound which is 330 meters per sec. So let me dilute the criteria for this imaginary police sniper rifle and say I want a muzzle velocity of 300 meters/sec (about 1000 fps) for a 20 gram (edited: 308 grain), 0.3 inch (7.62 mm) "pellet"

I am assuming a barrel length of 20 inches (50 cm). The pressure in the air tank is 3000 psi (or about 211 kg/sq cm)

My calculations tell me that this is easily achieved. In fact with a pressure of 3000 psi it should be possible to squeeze out at least 400 to 450 meters per sec (or 1500 fps), perhaps with a lighter bullet/pellet

Subject to error corrections in my calculation, I believe it should be possible to design a sniper rifle effective in urban areas for ranges like 150 to 200 meters at least. These ranges are probably useless for the military, but are still in excess of what is available off the shelf as hunting rifles. I will work on my calculations further but will need time because I am beginning to reach some hurdles when I step beyond these figures.

[timmy]

Bennedose, may I offer:

a 20 gram bullet = 308 grains

http://www.unitconversion.org/weight/gr ... rsion.html

The Quackenbush gun you linked works out to about 255 ft-lbs at the muzzle, considering 800 f/s @ 180 grains

http://www.1728.org/energy.htm

Your assumption that pushing a bullet over the speed of sound requires a great deal of energy compared to subsonic bullets is, I believe, correct.

Quackenbush could use a bullet a lot more ballistically efficient than a pellet, I think.

[bennedose]

Sorry Timmy - that was a typo. I did all my calculations using grams and simply typed 140 grain. I actually meant to type 280 grain for 20 grams - but that figure too is lower than yours. Google tells me that 20 grams is 308 grains as you say. I will edit the original.

I will need to go over my calculations again but the pressure needed for 300 meters/sec for a 20 gram projectile was just 100 kg/sq cm, while 3000 psi is approximately 211 kg/sq cm. So I guesstimated that 3000 psi should be enough to squeeze another 100 to 150 meter per sec out. Not sure though and I will recheck my figures unless someone else points out gross errors before that.

[timmy]

I don't know much about this subject, but I wonder if Quackenbush chose a spherical ball because it doesn't have very much area bearing on the rifling. There may also be something to do with the amount of surface area that a large bore presents to the pressure involved in the choice of .50 caliber.

If it is a matter of bearing area, I remember a bullet that had a "wasp waist" so that only a small area near the base and one right near the ogive bore on the rifling.

If it is a matter of surface area, perhaps a large bore could be used with a sabot, and a smaller diameter projectile with better exterior ballistics could be used.

Just wondering?

[bennedose]

I don't know much about this subject, but I wonder if Quackenbush chose a spherical ball because it doesn't have very much area bearing on the rifling. There may also be something to do with the amount of surface area that a large bore presents to the pressure involved in the choice of .50 caliber.

If it is a matter of bearing area, I remember a bullet that had a "wasp waist" so that only a small area near the base and one right near the ogive bore on the rifling.

If it is a matter of surface area, perhaps a large bore could be used with a sabot, and a smaller diameter projectile with better exterior ballistics could be used.

Just wondering?

+1
Brilliant. Will post some thoughts later

[TwoRivers]

"No please. Do not confuse lethality with giving up of energy."

"giving up of energy". Now that's a new concept.

''A bullet that passes through and makes a clean hole retains some energy as it flies out and fails to give up all its energy in the target."

And a bullet that doesn't make it all the way through must have had less energy to begin with.

" An exactly similar bullet that perhaps hits some embedded hard structure and tumbles and fails to pass through gives up all its energy."

Now you are changing variables. One bullet encounters some embedded hard structure, or tumbles. The other passes through without encountering anything hard, or tumbling.

"This is elementary physics and cannot be changed. In neither case does the target have to be an animal. It could be a bundle of cloth or a lump of silicone."

Only that one of those bundles of cloth, or lump of silicone, has something hard in it, and the other one hasn't. Perhaps you ought to study physics beyond "elementary".

"Lethality is a completely different issue. Lethality is determined by the manner in which energy is absorbed by tissues and which specific tissues absorb the energy. Not by size or energy of bullet."

So what then happens to that "energy absorbed by tissues" ? So maybe the problem with the 5.56x45 is that the Taliban have tissue that doesn't absorb energy very well.

"I do not want to talk about lethality simply because it introduces yet another variable for this thread. The variables I am talking about are
1. Design of air weapon for military/police
2. Characteristics of bullet/pellet
3. Conditions that increase the possibility of lethality

The last is least relevant to the topic.

"

Seems to me that "lethality" is something that's of great importance to the military when picking a cartridge and bullet.

[brihacharan]

> My query re: arming the military with Air Rifles....
Q. What about the logistics of carrying huge / portable "Scuba Tanks" to refill the air reservoiors on the field - after the soldiers fire a volley of say...50 to 60 'Pellets'

> Come to think of it - Firearm Ammo can be air dropped - Can one do the same with huge Compressed Air Cannisters
> Imagine the parachute coming down with a huge air cannister & the enemy takes a pot shot at it -....
> It would be a rib tickling sight to see the cannister whoooooshing like a witch riding her broom a la Harry Potter movie
Briha

[bennedose]

Seems to me that "lethality" is something that's of great importance to the military when picking a cartridge and bullet.

I am sure you are right. I would be happy to discuss what I know about lethality in an appropriate thread, but I do not intend to discuss it here. Lethality is a separate subject in its own right but that subject crops up only after power and accuracy which is all I am going to concern myself with here. Sadly I am unaware of the breadth of your undoubtedly vast knowledge about lethality, and would be happy to learn from you and share the little knowledge I have on the subject of firearm trauma should you choose to start off a discussion about bullets and lethality.

[essdee1972]

Tranquiliser gun with quick acting neurotoxin? Death by poison instead of by "massive injury to internal organs"? Some kind of toads have poisons which kill in milliseconds, I believe? Because you also need to ensure that the hostage taker does not get a "death grip" on the gun, resulting in spraying bullets all over the place.

Even I am of the opinion that firearms are the way to go, but if there's an interesting problem, why not exercise the grey cells? A welcome break from Excel & PowerPoint!!!

[bennedose]

Tranquiliser gun with quick acting neurotoxin? Death by poison instead of by "massive injury to internal organs"? Some kind of toads have poisons which kill in milliseconds, I believe? Because you also need to ensure that the hostage taker does not get a "death grip" on the gun, resulting in spraying bullets all over the place.

Even I am of the opinion that firearms are the way to go, but if there's an interesting problem, why not exercise the grey cells? A welcome break from Excel & PowerPoint!!!

I think that is a great idea actually. Someone said what if only a fingertip is knocked off by a bullet. Well fine. If the fingertip gets that poisoned dart then its curtains for the chap attached to the fingertip.

I just wonder if a dart can be designed to penetrate the fabric of body armour? A dart can be sabot discarding AND have vanes - like a spin stabilized sabot discarding anti tank round. Maybe cobra or krait venom? Or simply cyanide?

[essdee1972]

You would need neurotoxins to prevent the death grip. Haemotoxins wouldn't be so fast!

[brihacharan]

Bennedose wrote.....
I am sure you are right. I would be happy to discuss what I know about lethality in an appropriate thread, but I do not intend to discuss it here. Lethality is a separate subject in its own right but that subject crops up only after power and accuracy which is all I am going to concern myself with here. Sadly I am unaware of the breadth of your undoubtedly vast knowledge about lethality, and would be happy to learn from you and share the little knowledge I have on the subject of firearm trauma should you choose to start off a discussion about bullets and lethality.

> A bit of googling revealed this.....

Ballistic trauma
The term ballistic trauma or gunshot wound (GSW) refers to a form of physical trauma sustained from the discharge of arms or munitions.[1] The most common forms of ballistic trauma stem from firearms used in armed conflicts, civilian sporting, recreational pursuits and criminal activity. Ballistic trauma is sometimes fatal for the recipient, or causes long term negative consequences.
1 Destructive effects…
The degree of tissue disruption caused by a projectile is related, to the size of the temporary injury Vs permanent injury it creates as it passes through tissue. The extent of cavitation, in turn, is related to the following characteristics of the projectile:
Kinetic energy: KE = mv2/2 (where m is mass and v is velocity).
This helps to explain why wounds produced by missiles of higher mass and/or higher velocity produce greater tissue disruption than missiles of lower mass and velocity.
The immediate damaging effect of the bullet is typically severe bleeding, and with it the potential for hypovolemic shock, a condition characterized by inadequate delivery of oxygen to vital organs. In the case of traumatic hypovolemic shock, this failure of adequate oxygen delivery is due to blood loss, as blood is the means of delivering oxygen to the body's constituent parts. Immediate effects can result when a bullet strikes a critical organ such as the heart or damages a component of the central nervous system such as the spine or brain. Common causes of death following gunshot injury include exsanguination, hypoxia caused by pneumothorax, catastrophic injury to the heart and larger blood vessels, and damage to the brain or central nervous system. Additionally, gunshot wounds typically involve a large degree of nearby tissue disruption and destruction due to the physical effects of the projectile. Non-fatal gunshot wounds can result in serious disability.
Gunshot injuries can vary widely from case to case since the location of the injury can be in any part of the body, with wide variations in entry point. Also, the path and possible fragmentation of the bullet within the body is unpredictable. The study of the dynamics of bullets in gunshot injuries is called terminal ballistics.

>IMHO - This is an highly involved & debatable subject -
Briha

[bennedose]

If it is a matter of surface area, perhaps a large bore could be used with a sabot, and a smaller diameter projectile with better exterior ballistics could be used.

Just wondering?

Sabot discarding sounds like the way to go - and the same sabot could house different rounds - maybe even a dart?

The Quackenbush review says that the ball was accurate - but I doubt if spheres will remain accurate as they fly. There was a picture somewhere of a round with a couple of "waist rings" to engage the rifling. But still the sabot thing could be designed to accommodate more than one design of projectile I guess.

I actually have "Sabo" 0.22 pellets left over from a box I bought in the UK nearly 30 years ago. But I don't have a place to test them over ranges more than 20 meters. They are very fiddly and cumbersome to load. I wonder if anyone still makes them or if anyone has any use for them in the air rifle community?

[bennedose]

>IMHO - This is an highly involved & debatable subject -
Briha

Briha - dealing with ballistic trauma is something that I have to do from time to time in order to be able to afford to spread the enjoyable butter and jam of shooting sports on the bread of my life.

[bennedose]

You would need neurotoxins to prevent the death grip. Haemotoxins wouldn't be so fast!

I think an 18 gauge needle could be designed to project out on impact and penetrate clothing. The impact and deceleration could possibly be used to push the needle and toxin forward. Have you any ideas about the actual design?

Let me search for info...