Spring Air Rifle Dieseling

[brewman]

First up sorry for the long post.

The other weekend a friend and I went to punch some paper with our rimfires and I thought I would take my Remington Genesis air rifle with me.

I had not ever lubed the piston and though I would use a small squirt of silicon lube sprayed into the chamber, gave it a quick squirt, broke the barrel to operate the piston and distribute the silicone 5 or 6 times. I then left the rifle standing vertical for about an hour with the barrel standing on a rag to let any excess run out.

Off to our shooting spot. Set up our rests etc and my chronograph. After a few rounds through the rimfire I thought I would have a go with my air rifle.

Well first shot gave a hell of a muzzle report and the sonic crack of the pellet down range sounded like a high velocity rimfire, looked to the Chrony and I was gob smacked to see 1510 fps, what the hell, next shot 1480 fps. Now normally the Genesis is good for between 850 to 950 fps. Then it dawned on me “Dieseling”. After about 4 or 5 shots it was back to normal velocities.

I have heard of spring air rifle dieseling when the piston is lubed with mineral oil and because of this most information recommends high flash point silicon oil is to be used for piston lube, I did not think dieseling would have this much effect though.

I used to have an old springer years ago and would put oil down the chamber now and then to lube the piston it would smoke for a few shots after but never gave anything close to what the Genesis did with silicone spray.

Since the weekend I have searched a bit and apparently some people deliberately put flammable material eg diesel, lighter fluid etc in the skirt of their pellets to intentionally cause dieseling and high velocities.

Has anyone experimented with this?
I know it has been discussed briefly before so sorry for any overlap.
http://thefiringline.com/forums/showthread.php?t=417875&highlight=dieseling

Sounds like a recipe for disaster to me like broken main springs or even blown chambers, but sounds quite interesting too…..

 

[Slopemeno]

It's a bad practice. Since the advent of synthetic piston seals the need to put anything in the compression chamber has all but disappeared.

Find a good pellet it likes and sight it in. And practice.

 

[Sport45]

Putting fuel in the skirt may give you higher velocity but it won't be consistent. You won't know when you pull the trigger if you're launching the pellet at 900 or 1500 fps and at 900 the pellet is heavier by the weight of the fuel.

This inconsistency, along with the potential damage to the gun would keep me from trying it.

 

[kozak6]

Sounds like a recipe for disaster to me like broken main springs or even blown chambers

Basically. The seals and piston can be damaged too.

Yes, accuracy is also likely to be terrible.

Another issue that airgun pellets weren't designed for this. There might actually be enough umph to blow the head off the skirt. This may result in a bore obstruction, and maybe a ringed barrel if you fire again afterward.

Has anyone experimented with this?

Yep. The Weihrauch Barakuda EL54, a German air rifle, had a mechanism for injecting ether into the compression chamber. Round balls were recommended since it blew pellets apart. It burned through seals like crazy and the difficulty in obtaining ether made it rather unpopular.

Daisy also released a tremendously interesting "airgun", the VL. It was a conventional spring piston air rifle, except the pellet had a charge of gunpowder ignited by the heat of compression. It had performance comparable to a .22 lr.

 

[Skans]

I've experienced some dieseling in my Chinese B21/22 (copy of RWS 48). It comes with lube all over the place, and some gets into the chamber. Diesling tapers off with successive shots. I've never damaged any of the seals. I doubt very seriously that you could damage the piston or other metal parts on this gun - its built like a tank and the metal parts are more comparable to what you might find on an open-bolt Sten, rather than a Ruger Mark II.

I'm sure if you are putting fuel in the chamber to make it diesel, you will eventually destroy the seals. Seals are cheap and fairly easy to replace for me on my B21/22, so I really don't worry about this.