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AJAX22
10-16-2008, 5:45 PM
Ok people,

Here is a thought….

Air rifles can be converted into real firearms; it is regularly done in countries which have severe limitations on the ownership of firearms. Most conversions consist of taking a standard break action spring powered air rifle and converting the spring piston into a bolt with a small firing pin attached and boring a .22LR chamber using a 15/32 drill bit.


Its crude, but it works better than a standard air rifle would and puts small game on the table.
However… converting air rifles into conventional firearms is a bit of a hassle, requires decent tooling and would (in our state) qualify as a zip gun.
How then can we extract more knock down power from our air guns?

According to a study I read (sorry I don’t have a link, It was late and I didn’t save it) the accidental dieseling which occurs in standard air rifles as a result of flammable lubricants being compressed can provide up to 30% of the muzzle energy realized by the pellet. In fact a firearm platform which used this phenomenon as an ignition system was the Daisy VL, which compacted nitrocellulose against the base of a .22 bullet with no casing and used a high powered piston to compress air and ignite the propellant.

http://i166.photobucket.com/albums/u115/Ratduster77/pix2295314906.jpg

It worked great, but did not catch on and was only manufactured from the late sixties until the early 80’s (you can still buy them along with ammo but it costs a little more than standard rim fire rounds)

The purposely induced dieseling effect (as well as the resultant explosion of the propellant) in the VL system required the design to be much more robust than a standard air gun, as the sharp pressure spike of even the dieseling by itself in modern air guns can be enough to blow the seals and damage the mechanism.

It is because of the delicate internal nature that air guns cannot be simply converted to .22 VL by cramming a round of Daisy VL ammo into the bore (or reaming a chamber into the gun). The detonation would rapidly damage the rifle, and possibly injure the shooter since the gasses would be directly impinging on the piston and seals of the rifle itself. (on the .22LR converted air guns the brass of the .22LR case works along with the modified bolt to seal and contain the gasses)

So, in order for propellant to be added to a standard pellet, it would have to be slow burning, clean and relatively low pressure. This, in a standard rifle design, would mean that any improvement as a result of the propellant addition would be modest at best.
So…. We need to think outside the box… we need a low pressure slow burning propellant which can be added to the back of a lead projectile, but which will accelerate the projectile up to supersonic speeds to aid in the kinetic energy transfer at longer ranges.
We need a Gyro jet!

http://i166.photobucket.com/albums/u115/Ratduster77/gyrojet1960-04.jpg
http://i166.photobucket.com/albums/u115/Ratduster77/GyrojetVLairgunconversioncartridge.jpg
We can fashion an outer casing from an expended .22 Magnum casing and swag it into shape using a modified bullet jacket swaging tool (they make ones already which turn .22LR casings into .224 diameter casings, so with some slight modification to the shape and diameter it would be easily possible to make one which fit without issue into a standard .22 Air gun bore.


Since the brass itself is not heavy enough to inflict much damage, we can take a few balls of lead shot and put them in the swaged casing, heating them with a small torch until they melt, evenly filling the tip of the projectile.

The main portion of the casing can be packed with either a KNO3 and sugar compound (rocket fuel) or an alternative clean burning solid propellant. Once tamped in place a combination sealant and priming compound (not sure what would work best yet, possibly nitrocellulose) can be added to cap off the round and aide in ignition.

The resulting round could be loaded into a standard .22 cal air rifle (or a more specialized platform could be developed later on) and upon firing, the blast of hot air generated by the spring piston would ignite the priming compound and fuel mixture which would have the effect of both eliminating vacuum drag (like a bottom depleting tank round) and increasing acceleration past the supersonic threshold.

Unlike the gyro jet , since the actual spin would only be imparted to the round by the rifling engaging the casing, it would be able to avoid some of the problems that the original gyro jet had as a result of clogged vents sending stray rounds off course.
http://i166.photobucket.com/albums/u115/Ratduster77/gyro5.jpg
Anyone want to make a prototype? I can’t do it where I’m at… NYC would Sh*t a brick sideways if I tried to play with this stuff here.

I think I can modify this pelet gun to take these rounds and feed from the magazine.

http://i166.photobucket.com/albums/u115/Ratduster77/pix2381333937.jpg

tow4dough
10-16-2008, 8:19 PM
whoa....is your real name MacGuyver??

Rudolf the Red
10-16-2008, 8:34 PM
Damn, you are serious about this.

More power to you.

Maser
10-16-2008, 8:58 PM
Cool little project there, but IMHO looks like more work than worth it. But that's just me.

dribbler
10-16-2008, 8:58 PM
but why?

dwtt
10-16-2008, 9:35 PM
I hate to rain on this idea, but in order for the hot transient blast of compressed air in an air rifle to ignite the priming compound, the priming compound has to be relatively flammable. Such a primer would not be something you would want to carry around.

CHS
10-16-2008, 9:45 PM
but why?

Because: Awesome.

That's why.

gun toting monkeyboy
10-16-2008, 10:01 PM
hit the wiki entry for gyrojet. There is a link to a guy that is trying to re-invent them. I don't know how far he has gotten, but his links were still active the last time I hit them.

-Mb

saki302
10-17-2008, 3:48 AM
Did you know on the original gyrojet, if you put your finger on the muzzle, you could catch and hold the bullet there, liek a cartoon? It's the only firearm on earth which has increased muzzle energy FURTHER from the muzzle!

The only way to make it practical would be to make it 1/2 function like a regular bullet, with a rocket to boost velocity downrange. But the gain is probably not worth the complexity.

Is the Daisy VL considered a firearm? I'm guessing it is?

-Dave

6079Winston
10-17-2008, 1:53 PM
Not that I want to discourage out of the box thinking, but this might be a zip gun, incendiary ammunition, exploding bullet, rocket launcher or some multiple count indictment in Ca. A muzzleloader conversion might be OK with percussion cap ignition, with .32-.36 cal being the normal minimum bore size. Any attempt to use dieseling to ignite a loose powder charge might aeresolize the propellant causing detonation and fallapart.

AJAX22
10-17-2008, 3:19 PM
There are a number of compounds with a low flash point that are safe enough to handle, the original Daisy VL is proof positive of this, (no one has ever reported a mishap with any of those rounds)

It probably is a lot more work than is really necessary, but it would allow us to take something that we already have cheap easy access to and use it more effectively.

This wouldn't be anything different than existing gyro jet pistol technology adapted to a smaller longer design and ignited by hot air instead of a percussion cap, so it shouldn't be treated any different under CA law than the existing gyro jet firearms.

The powder charge wouldn't be loose, it would be a solid fuel rocket motor and a solid priming compound/sealant. It is actually fairly critical that the propellant be solid to regulate burn rate.

The airgun would already have a muzzle velocity of 500-1000fps, the propellant would kick that up significantly accelerating it downrange as it progressed

I believe The daisy VL wasn't initially considered a firearm but it was re-evaluated by the BATFE at some point and now is.

Spearo
10-18-2008, 11:35 AM
Wow, are you gonna build your own jet-pack next?:D

elsolo
10-18-2008, 12:17 PM
It seems like it would much less consistant than a metallic cartridge, high powered airgun, or blackpowder gun in every possible way; and much more of a hassle too.

Shooting a bottle rocket with a lead nosecone out of a spring-piston airgun

DrunkSkunk
10-18-2008, 2:38 PM
I would say get a better air rifle. Mines makes splinters out of 2x4's, completely blows through them. Blows right through STEEL 55 gallon drums as well.

AJAX22
10-18-2008, 3:51 PM
Well yeah, but wouldn't it be cool if you could take your whoopass 2x4 splintering air rifle and stick a cartridge in it that radically extended the lethal range?

I'm not saying that we need to abandon Air rifles or that firearms are outdated and need to be replaced, I'm just saying that it would be neat to have an ammo option which would allow for us to increase the lethality of a non restricted item.

NeoWeird
10-18-2008, 4:36 PM
Why not just replace the piston with a breech block with a striker inside. Then you can just ream the chamber accordingly. Heck, you MIGHT even be able to get away with a .177 cal barrel with .17HMR.

Sadly, what you describe WOULD be a firearm and it most likely would be considered a zip gun. You also didn't address the problem of hot gases going back into the seal area of the gun because with your drawing the case would only seal the walls; not the rear portion.

If you ask me, if would be 1,000 times easier, and cheaper to boot, to make a single shot firearm yourself using a piece of steel pipe/tubing and fabricating a bolt and locking mechanism. Now you might be able to use a air gun barrel, but outside of that, you're pushing it price wise already.

You have to remember that most air guns of quality that could safetly withstand firing a bullet are already $50-100, so by the time you invest another $50 in material, the $300 to make these cases, and your time - you're already pushing the price of a accurized Ruger 10/22 Magnum converted to .17HMR with decent glass on it and ammo would be cheaper and easier to get as well.

It's a great concept for countries that have super strict regulations, but we're not there yet so we have better options.

I like your line of thinking though. I truely admire what you do and try to do, Ajax.

AJAX22
10-18-2008, 7:13 PM
I've scratch built guns before, ... and I could easily adapt the existing bolt on a standard barrel brake .22 or .177 air rifle into a breach block assembly, but that's been done... its quite simple, most shotgun and pistol rounds do not create enough pressure to require a locking mechanism for the breach, having a small spring and sufficient mass is typically all that is required.

I think the whole idea is really to create a new type of ammo which can be fired from any conventional air rifle (spring compression type) without modification.

Because of the low pressure nature of slow burning rocket propellants it wouldn't have to be a very high quality air gun to hold up.

I don't think the problem of the hot gasses going back into the seal area is as big of an issue with a non explosive cartridge, It wasn't the hot gasses that destroy the air rifle seals, but rather the high pressure generated by the cartridge.

My experiences here in NYC have convinced me that keeping the technology a step ahead of the legislators is absolutely necessary. The bb gun itself is already illegal here (as it is in a number of states).

However, the rocket cartridge itself could theoretically be fired from any 1/4in brake line tube ignited with just a lighter.

I know that the bullet/air gun combo would be considered a firearm, but I believe the independent components would slip between the cracks of legislation (like the cartridge converted black powder guns)

In theory the existing gyrojet cartridges could be used without a firearm, they would just be hard to aim/control.

Thanks for the compliment, but there are a number of guys on here who do way more to actually get this kind of stuff built than I do. I just daydream a lot when I'm supposed to be studying ;).