What does dieseling mean? - Part 3
by B.B. Pelletier
Before we begin, a word to those who are having difficulty emailing Pyramyd Air. They recently changed their email program and the one they use now is more sensitive to blocking spam. Some ISPs (Individual Service Providers - the place where you pay for your internet connection) are known for their spam, and if the Pyramyd email software detects them, it may discard your email without giving you any status. If you can't get an answer, I recommend you call them at 888-262-4867. They have worked hard to reduce the phone wait time and, while it's still not perfect, hold times are much shorter.
Well, this three-part posting is turning out to be one of your all-time favorites. It seems we have a great number of spring gun fanciers in the audience.
Let's look at how a gun can be made to diesel intentionally, starting with the famous Weihrauch HW Barakuda EL54. That was a standard breakbarrel rifle, the HW 35, to be specific, with a tube on the right side to inject a small shot of ether vapor into the compression chamber just before the shot was fired. I covered it in a special post last year, so you can read all about it there if you want to. The point is thst manufacturers recognized the power potential of a detonation and tried to harness it to make airguns shoot faster. Today, we would call the EL54 a firearm, because that is exactly what it is.
You don't have to be an airgun manufacturer to make a spring gun diesel. Now that you know how it works, you've probably figured out it takes just some fuel coming in contact with the superheated, compressed air generated by the piston. Children have known this trick for at least half a century, which is the basis of the Oil-Can Louie story I mentioned in the previous post. However, that story ends with the destruction of the airgun, so please don't experiment that way.
Deception through dieseling
Gamo sells a .177 breakbarrel spring rifle called the Hunter Extreme, which they claim is capable of generating 1,600 f.p.s. with PBA pellets. When a friend of mine chronographed his, it was shooting just over 1400 f.p.s. Many of you know that I asked for any reader with a Gamo Hunter Extreme to chronograph their rifle and to tell us the numbers. To date, no one has come forward. Gamo used to show a film clip on their website from the Shooting USA TV program that shows a shot chronographed at more than 1600 f.p.s. I tested a PBA pellet in a .177 Condor and it went only 1486 f.p.s., which tells me something might be fishy about Gamo's claim. However, it is possible to make a pellet go as fast as that televised shot with some trickery.
All it takes is a pellet with a partial drop of a volatile substance like diesel fuel in its hollow base and you will get velocity figures like that. Forget accuracy at that speed, but the velocity will be there. That's all some people want to see. The gun may not hold up long with that kind of abuse, and I do not recommend that anybody attempt it. As far as I know, this is the only way to get a pellet from a spring-piston airgun going that fast without extra mechanisms, such as an ether injector.
Daisy used the principle, too!
In the late 1960s, Daisy put the caseless cartridge of Jules Van Langenhofen into production in a rifle that ignited the solid propellant using the heat of rapidly compressed air. Theoretically, their gun was a .22 caliber spring-piston rifle that just happened to shoot a caseless .22 as powerful as a conventional long rifle. In practice, the bore was too large for pellets, and any .22 pellet you tried to shoot in it was hopelessly inaccurate as well as being underpowered from all the blowby. Guns that use the VL system are still popping up at airgun shows, where they now command $150-225, depending on condition. The cased presentation models have always gone for more.
How to stop the detonating
Apart from specific Webley and Weihrauch guns that have piston seals made of PTFE, stopping a spring gun from detonating is iffy. Some guns seem to detonate more than others. Cleaning the compression chamber and lubricating with a small amount of the correct lubricants is a surefire way, but it involves disassembly of the powerplant. You can sometimes solve the problem by putting a drop of high-flashpoint silicone oil into the chamber through the transfer port (or the oil hole in the case of a Mendoza). The high-flashpoint oil seems to dilute the other oils and greases to the point that they diesel but no longer detonate. This isn't a positive solution, but I have seen it work.
Well, that turned out to be a longer answer than I thought it would be. But, now, when the subject of dieseling comes up, we have a place to turn to.