Air Rifle velocity increase.

[GrOuNd_ZeRo]

Today I was experimenting with some WD-40 in my Shadow-Matic, I know it's bad stuff for a gun but for fun I just put a bit in the skirt of the pellet, to my suprise the air and WD-40 create a diesel effect and launches the pellet at super-sonic speeds (the Matic fires at 850 FPS normally), I don't know how much of the WD-40 ignites and how much residue is left in the barrel it self but it produced a nice super-sonic crack, unfortunatly it affected accuracy negatively by a marginal amount.

On another note, Gamo produced a premium "Raptor" pellet made out of gold to accellerate their pellets to super-sonic speeds even in lower powered airguns, I wonder if it will have a similar effect and destabilize them since anything over 1200 FPS will destabilize a pellet (or so I heard) which the gamo Raptor pellet will accellerate in on a 1000 fps air rifle.

Would I recommend using WD-40 on your pellets? No, but my airgun is already in a less favorable state due to some inexperience on my part in airgun maintenence (I.E. I cracked the polymer stock's fore-arm when I tightened the screws too much and some of the metal rusted a little since I didn't use gun oil or cases to protect in from moister).

I thought it would be fun to experiment with an airgun that already has no resale value, the WD-40 did make shooting it a little more entertaining esspecially on the candle I was shooting at since it made explode in messy parafine all over the place.

So it that old rusty airgun of yours is no fun, perhaps WD-40 will give you that extra kick you were looking for!

 

[colt.45]

interesting.... i think ill go try it.

 

[mec]

Daisy VL. They ( or a guy named Jules Vanlanguenhoven) noted the venturi effect back in the 60s, installed a small vent nozzel to superheat the air and put a tuft of some sort of nitrocellulose on the bottom of the pellets. The air would ignite the material and it would go off with a supersonic crack.

 

[Owen]

be careful with the WD-40. It may eat your seals.

The crack doesn't indicate the pellet was supersonic, just that the pressure at the muzzle was much higher than you are used to.

If you really want to know, you need a chronograph

 

[RyanM]

Sigh. Compressed air will not make WD-40 burn, explode, or much of anything else.

 

[JohnKSa]

Pressures inside a spring-piston airgun chamber can peak briefly around 1400 psi. Physics tells us that compressing a gas causes the temperature to rise--in this case temperatures can exceed 1000 degrees F for a very brief instant.

That is certainly WELL above the flashpoint of most petroleum products which is why spring-piston chamber lubricants are petroleum free. WD40 is more than 95% petroleum products so it is definitely a bad idea to put it in your airgun compression chamber.

Intentionally introducing large quantities of flammable materials into the chamber will cause detonation or severe dieseling which can damage the gun (even to the extent of bulging or rupturing the compression chamber) and, in extreme cases, even pose a danger to the shooter.

That is besides the damaging effect that some solvents can have on the seals in a spring piston airgun.

In addition, the value of the extra power gained by this detonation effect is minimal since the accuracy will be very poor.

 

[GrOuNd_ZeRo]

I most definitely did not put any in the compression chamber however i'm sure the seal did get effected by it.

 

[JohnKSa]

The back of the pellet is effectively part of the compression chamber. I suppose that if you fire very quickly after loading, very little of the flammable material will have time to migrate into compression chamber proper. That might prevent you from rupturing or bulging the chamber. Dunno...

 

[230RN]

SPRING AIR GUN DIESELING

Many years ago, I found my Feinwerkbau .177 delivering an exceptionally loud report.

The pellets penetrated a previously secure backstop, and the smell of a diesel bus hung around the room for a while.

I wrote to the NRA Questions and Answer section about this and although I cannot document this any more, the upshot was:

1. The compressed air in powerful spring air guns can reach over 1000 degrees Fahrenheit, and can indeed ignite the oil spray which is inevitable when the piston moves up the compression chamber.

2.This phenomenon is minimized with proper lubrication.

3. The phenomenon is variable, and usually results in inaccuracy due to the uncontrolled pressure variations as the oil is consumed.

4. There were some designs of military air guns which took advantage of the extra velocity obtained by the dieseling effect, where extra fuel (oil) was automatically placed in the compression chamber before each shot.

5. Unless the air gun is designed for it, this dieseling effect can be destructive to the seals on regular airguns.

I was also later told by an airgun expert that peanut oil is less susceptible to the dieseling effect, but to use the factory recommended amount and type of lubricant anyhow.

 

[FLORES425]

seals?what will happen?

 

[albanian]

"Sigh. Compressed air will not make WD-40 burn, explode, or much of anything else."

You got that wrong. Many different oils will diesel in a spring piston airgun. It happens all the time when someone puts too much oil on their gun. The effect is called "detonation" and anyone who has shot high powered springers knows all about it.

I have a Running Deer that I have never oiled that will diesel for the first few shots if I haven't shot it in a while. I really should clean out the chamber but I don't want to open it up unless it becomes a problem. More airguns are ruined by people trying to fix them that anything else I suspect.

 

[230RN]

SPROING-CRACK!

Flores : "Seals? What will happen?"

First of all, they will be stressed over their design pressure and design temperatures by the oil burning.

Second of all, the products of combustion of the oil vapors / spray are largely unpredictable, and lower fractions of the combustion products may tend to dissolve, soften, or otherwise damage the seals.

Third of all, one of the combustion products is amorphous carbon, which will collect in both the compression chamber and in the bore of the air rifle. Carbon is mildly abrasive, and will tend to wear out the elastomer of the seals.

Although some carbon also collects in powder-actuated firearms, there are no elastomeric seals in regular firearms, and the carbon has little or no abrasive effect.

In re Albanian's remark about cleaning:

"More guns, cameras, small boys and coffeepots have been ruined by excessive cleaning than any other single cause." ( --Dick Valentine, ca 1968)

 

[JohnKSa]

Flores425,

Pump-up airgun internals do not reach the same temperatures as spring-piston airguns. However, the seals are still subject to damage from using firearm type oils which may contain solvents. It's always best to use airgun specific cleaning and lubrication products rather than trying to improvise.

 

[Zero_DgZ]

Sigh. Compressed air will not make WD-40 burn, explode, or much of anything else.

Oh yes it will! I don't think you understand the sort of pressure increase, friction, and heat buildup going on in a spring piston air rifle.

 

[230RN]

FIRE PISTONS

Lest anyone disbelieve how hot suddenly* compressed air can become, I've found a couple of links to what is known as a "Fire Piston."

With this device, you place a small amount of tinder on the end of the piston, place it in a tightly-fitting cylinder, and ram the piston down to the end. When you pull it out, LO ! the tinder is burning!

Just for grins, my son made one of these out of some of that brass tubing you can buy in model shops, and it even works at our high altitude in Colorado:

http://www.hollowtop.com/hopsstore_html/fire_pistons.htm

http://www.firepistons.com/catalog1.0.html

(On this second link, scroll down to the bottom of the page and click on "How They Work.")


------
* The qualifier is "suddenly," which is why spring operated air guns diesel, but pump-up ones do not. While the air in a pump-up air gun gets warmer on successive pumps, the heat is quickly dissipated to the metal of the pressure reservoir.

 

[GrOuNd_ZeRo]

A few things about my rifle.

It's a Gamo Shadow-Matic, I Think it's capped to 850 FPS but it's actually based on the 1000FPS model (VERY high amount of parts commonallity), what's interesting about this design is that it has an automatic loading system and it actually seperates the piston and the barrel where the pellet is housed so I think there shouldn't be much chance of the WD40 and Charcoal lighter (which I used recently) to enter the chamber, also
too little combustable material is used and should all be ignited upon firing (I just dip it in WD40 or charcoal lighter).

Accuracy is actually good when I do it when I tried it, I zeroed the iron sights and the velocity definitly does increase since it shoots straight through my backstop!

Another interesting experiment I did was put a few BB's down the barrel to get a shotgun effect, they aren't launched at high-velocity but it's still fun, I wouldn't reccomend it though since the barrel isn't made for BB's.

Don't the Mexicans have these air rifles that shoot firearm cardridges or something? I don't know exactly what they shoot but I heard about them a while ago.

 

[Giolli Joker]

4. There were some designs of military air guns which took advantage of the extra velocity obtained by the dieseling effect, where extra fuel (oil) was automatically placed in the compression chamber before each shot.

Interesting...

 

[colt.45]

ive got it!!! instead of using wd-40, put some vaseline on the skirt of the pellet. it is thick enough so that probably wont get on the seals. its late so i'll try it tomorow. boy this'l be fun

 

[colt.45]

well... the petroleum jelly didnt work. but i did find that silicone lubricant makes a pretty loud crack.

i fired a dry q-tip at the ground and it stuck into the dirt smouldering, but only for a second. more tests tomorow.

 

[mrmeval]

Bead a drop of 91% alcohol in the back of the skirt. Now try kerosene.

 

[230RN]

SUNDAY MORNING RUMINATIONS BEFORE THE COFFEE GETS TO WORKING.

Hm. Wonder how a wooden match would work? You try it, not me. Fire danger reeeeel high out here in Colorado. Besides, I value the rifling on both my spring air rifles too highly. Glad you have a throwaway to do your testing.

How about shooting a small rifle or pistol primer through it? You try it, not me. I'm a certified coward.

I wonder about using silicone oil. I suspect one of the combustion products would be silicon dioxide, i.e., sand.

Which is highly abrasive.

Sure is more fun reading about these tests than doing them.

By the way, with regard to the Mexican spring air rifles, I mentioned above that some military air rifles took advantage of the dieseling effect by deliberately putting some fuel in the chamber automatically before each shot. I haven't looked it up, but the name Mondragon seems to stick in my wrinkled old cortex on that subject.