Hiya, fellow DIYers and airgun enthusiasts! NK here with a quick pellet hack to increase pellet velocity in mid to high velocity springer (break barrel) air rifles.
Spring air rifles work by pushing a spring into a locked position. The spring is released and pushes a piston forward, propelling a pellet out of the barrel with air pressure. The sudden compression of air generates intense heat, like a fire piston.
A diesel engine uses the same phenomenon to get its power--it compresses air in a cylinder and injects fuel. The fuel burns, creating a movement of the drive shaft.
This principle can be harnessed for your pellet gun to increase muzzle velocity. (I suspect that in very rare cases that YOU SHOULD NOT TRY TO REPLICATE (You could lose your face. I am dead serious.) I seem to be getting more than 2 inches of penetration on a log (similar to a .22 LR) from a .17 cal. This leads me to believe that the round was traveling in excess of 2,000 FPS,more than double gun's normal power.)
You will need:
Peanut oil or vegetable oil
Alliteration! 3 P's
Springer/breakbarrel gun (Yes, nitro piston/gas ram (NOT CO2) works too, and you guys with gas systems, you can beat the hell out of your "spring" since it is just air, but you may damage seals. Otherwise, you may have few limits, aside from chamber rupture pressure.)
Put a few drops of peanut or other pant, not petrol oil (petroleum based oils dissolve seals which takes time and money to fix) into a tin of pellets. Shake. Put pellets out on paper towel. Carefully dab off extra oil. Load a pellet and fire. You should see some smoke when you fire. This is normal, and your gun probably does it naturally sometimes.
If you hear a very loud bang, either you have broken the sound barrier (common) or the oil has detonated (also common, and usually breaks sound barrier as well.) If your gun does not shoot over 100 fps normally, than this is bad. DO NOT DO THIS REGULARLY. It may be cool, but it is inaccurate, as the shock wave catches up with the pellet as it gets slower, making it tumble. It also can blow up barrels if repeated with a lot of fuel or very often. In less extreme detonations, it may recock (bad) or break the spring and main seals (also bad. Duh...) So just towel them off again until you get smoke but not a very loud crack.
If your pellet gun can shoot beyond the sound barrier with super light pellets, like raptors, than the loud sound is just a sonic boom and is fine. You should still tone down oil for accuracy's sake. If your gun can fire beyond sound barrier with normal lead pellets, than go ahead. You will be far enough above to get good accuracy with peanut oil. Probably better than without since the sonic boom takes longer to catch up to a faster pellet. But unless your gun can do it with whatever pellets you are using sans oil, don't. If your gun can break sound barrier with ultralight, still don't, because this coupled with ultralight is bad for spring. You can do this with a gas ram system, however, since they have no spring to worry about.
Step 1: Safety and Tips for Goin' Easy on Gun and Accuracy
1)Dry pellet by shaking and dumping on paper towel. Wipe off the inside of empty tin. Dab pellets. Put in tin and shake. Repeat until the pellets do not make a supersonic boom after firing ten shots. Shake tin avery five well aimed shots or every two very well aimed shots. Or just shake every two min. This re-disperses oil, resulting in more consistent muzzle velocity.
2)You will know a detonation when you hear one. It will usually come coupled with a supersonic crack, but unlike a normal supersonic crack, the initial bang is much louder. When a shot goes supersonic, two things make loud noises: the initial bang of gas escaping the muzzle, (that is the bang from a normal subsonic shit)
The second bang is the shockwave behind the pellet. The shockwave is what causes destabilization, as mentioned earlier. Anyway, in a detonation, the initial bang is very loud. You will be able to tell these apart, almost certainly.
When a detonation occurs, a great deal of force is exerted. I have had one shot where the skirt of the pellet was separated from the head. The head rocketed forward and went through an incredible two inches of solid tree. The skirt Flew out as shrapnel, but a little bit was forced through the thin crack created by the barrel meeting the powerplant. Molten. Inside the gun. Bad. Avoid detonation. really.
One more side note: The official definition of detonation is a combustion reaction that propagates faster than the speed of sound in a given substrate. I am not sure if this is what happens during and airgun "detonation" , but this is the most widely used term. If it were a true detonation, the brisance (shattering ability) is high. This means that a work hardened or high carbon steel may fracture and fly off in a badly designed gun.
I find it likely that it could indeed be a true detonation for two reasons: the gas all reaches ignition temperature at almost exactly the same time. This results in an incredibly fast ignition, and possibly a detonation. Reason two is that a gas deflagration (burn) can breach the sound barrier when it encounters turbulence (such as the constriction from pressure cylinder to barrel, as well as the skirt of pellet. Also, the chamber is so small by the time the gas ignites from that the flame probably rebounds across the chamber at unimaginable speed.