This report covers:
- The nitrogen experiment
- What the Cardews’ experiment really means
- Please forgive
- Intentional detonation
- What does BB do?
- Heavy pellets
Today we’re going to take a look at dieseling and detonation — two things that many shooters believe are bad. One of them is, and the other is inevitable.
Let’s begin with the comment of a new reader, tomek from Germany, who is Polish-born. He mentioned his Suhl 300 air rifle. I’m not familiar with that airgun, but it sounds like a neat little breakbarrel that Haenel might have made.
Regarding dieseling, here is what tomek said.
My experience with diesel effect: if you have a detotanation-like events you should dismantle the system and clean it right away. Waiting until the grease or oil will burn out is not a good idea. I own also a HW50 and once, due to my mistake, I had a really bad detonation which broke the spring and destroyed the piston sealing.
There is no point starting with chrono measurement if you can even smell burning grease. If it detonates – not at all… I’m pretty sure if you would clean the system and make a proper -grease finish again with only a silicone-oil film in the compression chamber the chrono results will be different.”
I used to feel the same way, until I read the experiment done by the Cardews — father and son, who wrote the book The Air Gun from Trigger to Muzzle.
The nitrogen experiment
The Cardews tested a .22 caliber Weihrauch HW35 that was getting 636 f.p.s. with a 14.4-grain pellet. They put the rifle in a large plastic bag and sucked out all the air. The left it that way for 30 minutes to get all the oxygen out of the piston seal, then they filled the bag with nitrogen, which doesn’t support combustion. The muzzle was poking out of the bag, but they resealed it with a plug after each shot. They shot this gun in a pure nitrogen atmosphere for several shots and recorded a velocity average of 426 f.p.s. The gun had only 45 percent of its initial power (energy, not velocity) when it was not permitted to burn fuel.
Then, they took the gun out of the bag and continued firing it and the velocity rose back to the initial figure. This is their proof that combustion happens with every shot. Not only that, but with some guns that have tight velocity spreads, it is also very well regulated!
What the Cardews were testing was dieseling, however, they also included detonations under the same title by labeling them “violent diesels.” The Cardews also did their experimentation at a time when 600 f.p.s. was considered normal for an airgun. This was in the early 1970s, when 800 f.p.s. was considered the maximum velocity a pellet rifle could achieve. It was even called the 800 f.p.s. “barrier.”
What the Cardews’ experiment really means
The Cardews don’t address this, but what their nitrogen experiment means is that in an oxygen atmosphere, something is happening that boosts the velocity of the pellet — and in many air rifles the boost is very consistent. In their experiment the boost was 210 f.p.s. What caused it?
They did determine that when the piston in the rifle they tested went forward, it stopped about 0.10-inches (one-tenth of an inch) or 2.54 mm from the end of the compression chamber. This stop was caused by the pressure of the air the piston had compressed to around 1,350 psi. That pressure caused the piston to bounce back off the high air pressure, which then lowered the pressure to around 1000 psi. That rebound was just 0.02-inches. That’s right, two one-hundredths of an inch.
When the compressed air expands from the piston bouncing back, the small oil droplets flash to vapor. If the adiabatic temperature (heat caused by compression and not long-lasting) remains high enough, this vapor instantly ignites, causing a diesel that’s no different from the one in Rudolph Diesel’s engine. This small explosion of igniting oil is called dieseling and it’s normal in spring-piston airguns. If it didn’t happen your 636 f.p.s rifle would shoot at 426 f.p.s.
I am broad-brushing the work that the Cardews did so I can explain a simple point. Most spring-piston airguns diesel on every shot. However if they shoot very slow — perhaps in the 400 f.p.s. range and below, like the Slavia 618s we have looked at — then they may not diesel at all, because the temperature of the compressed air is too low to ignite the oil. But even in weaker rifles like the Diana 25 and 27 it undoubtedly occurs.
The Cardews showed numerous pressure curves that showed the differences between a normal diesel and what they called a violent diesel and I am calling a detonation. Their term is more precise, because even the diesel is the result of a small explosion, or rapid oxidation of the air/oil vapor.
But the detonation is something more. A detonation is an explosion you can hear and even see if you shoot in a dark place. You will see fire coming from the muzzle of your rifle.
Now many believe that if you see smoke coming from the muzzle the rifle is detonating, but it’s not. My .22-caliber Diana 807s both smoke when fired and they have never detonated. A detonation may also have smoke, but it is the sound that is the determinant — either that or the chronograph.
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. The point is that 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 that 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 that’s in The Airgun Digest Volume 2. However, that story ends with the destruction of the airgun, so please don’t experiment that way.
Gamo sells .177 breakbarrel spring rifles that they claim are capable of generating 1,600 f.p.s. with PBA pellets. When a friend of mine chronographed the one he owned, it was shooting just over 1400 f.p.s. 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 oil-can Louie trickery.
What does BB do?
So, why did BB keep shooting the HW 50S if it was detonating? Well BB has worked on many dozens of spring-piston rifles and has a sense of how bad something might be. That doesn’t make him omniscient — BB makes mistakes all the time. That’s where a good number of his blogs come from. But he has a sense of whether the detonation is terminal or not, and he presses through if he believes it isn’t. It’s a risk I’m willing to take because I have seen it so many times. You do whatever feels right for you.
I have seen rifles that wouldn’t stop detonating and those I had to disassemble to correct. Many Chinese mega-magnums were like that. If the HW 50S hadn’t stopped detonating when it did I wouldn’t have continued shooting it much longer.
I have found that heavier pellets generate more back pressure and that stops the dieseling in guns that are going to stop all on their own. That’s why I started shooting RWS Superdomes after the lighter Falcons detonated. It stopped the detonations in about 4 shots.
That’s what I can tell you about dieseling and detonation. Now you talk among yourselves and we’ll all get smarter.
65 thoughts on “The difference between dieseling and detonation”
Wow! I’ve been viewing the whiffs of smoke coming from the muzzle of my TX200 after each shot, especially after the rifle has warmed up a bit. I haven’t known whether to be concerned or not, but now BB, you’ve addressed my worries. I love it when you answer my technical questions, as well as airgun reviews, as well as . . . gosh I’m addicted to this blog. Thank you! Orv.
This is where a chronograph comes in handy, too. I have a tuneup on the TX 200 Mk III coming soon.
BB: I’m devastated . . . I took it as gospel truth when you said that my TX200 was perfect right out of the box . . . and NOW you tell me that it may need a tune? I’ll be awaiting the news. Orv
Just something that popped in my mind. If taking away the oxygen made the guns velocity slow down.
Wonder what would happen if you added oxygen. What I’m thinking about is like when people use nitrous on cars to go faster. Nitrous is super cold oxygen. So if you have the right fuel mixture you get a bigger explosion in the cars combustion chamber.
Probably the same would happen in a air gun.
That would probably be too much of a big bang. Fortunately very few people shoot in an oxygen enriched environment (maybe inside a greenhouse?) for this to happen.
Makes me think that filling a pcp gun with nitrous instead of air would be a bad thing.
Well nitrous oxide is a provider of oxygen in comparison to pure nitrogen which is a relatively non reactive gas.
Not good. Bad. Big boom.
It could cause enough of a detonation to blow the valve open. I will let your imagination take it from there.
Yes. More oxygen will make a louder bang.
Wow thank you for such a good information. Such a fast response, respect! 🙂
The real detonation I had only once with HW50. This was destructive. My first airgun Suhl300 was always “smoking” as the seal was made of leather and needed oil to work properly. I never did chrono this rifle.
I had also two spring rifles which were generating smoke after each shot and the chrono results were very unstable. So my experience with smoking airguns is that they may not have a stable V0.
Example which I mentioned yesterday – my new Comet220 was full with some bad looking grease. It was all in the compression chamber, the spring and trigger were not greased at all… Anyway I learned to dismantle and do the “zero check” on each new spring airgun, does not matter what manufacturer made it. It was generating diesel smell without doing much smoke. Really badly. The chrono result was not stable. After I clean all up and put the stronger spring there was nothing dieseling after 10 shots. Only the first one generated some white smoke (I used silicone oil, only thin oil film). Now the V0 is really stable.
Tomek, welcome. I know 3 words in Polish, and the only one that seems remotely appropriate is: Yakshemash! Another one is Dziękuję for inspiring today’s blog. Hope to see your comments in the future. (I had to Google for the correct spellings).
Roamin Greco – thank you 🙂 Yes – jak się masz (how are you) sounds like this 🙂
B.B. and tomek,
My Diana 340 N-Tec smokes on almost every shot. Or should I say, when I break the barrel after a shot, there is usually a small amount of smoke that is emanating from the barrel leede. I always think it is kind of cool.
Is this a serious issue?
My 30’s era Webley Service MK II fills the barrel with smoke on every shot. I have been inside this gal and put a new bronze seal on her. I cleaned her good. She still smokes.
I told her she needed to quit smoking as it was not good for her, but she ignored me.
If the velocity is stable it sounds pretty normal and not a problem.
FWIW-Because it is a gas ram, and I was told to store the rifle with the ram’s stem pointing down; perhaps lubricant is seeping past the piston seal when the rifle is “asleep”?
I had a detonation with my Gamo CFX shortly after I had PA put a gas sproing in it. It was VERY loud with lots of smoke coming out the barrel and around the loading block. It had destroyed every seal in that air rifle and sent the little knob that rotated the loading block sailing through the air somewhere, never to be seen again.
Well, I packed it all up and sent it back to PA and they very graciously rebuilt my CFX, put the old sproing back in and refunded me. I’m a loyal customer.
They almost killed you, and you are a loyal customer?
Off subject just a bit. I was wondering if any company out there will be offering an adjustable gas spring in the near future? I do understand why companies stop offering such.
I am one of those individuals who would likely tune it down instead of cranking it up. I think I am one of those who would really enjoy a well made sproinger like a Theoben.
Vortek has one coming for the Diana 34 EMS.
Hey there friends and neighbors! There are some out there who have not been around long enough to know why RidgeRunner calls spring piston air rifles “sproingers”. Maybe this will help.
I’m glad you shared that. Now I know. :^)
If most springers are sproingers, then before B.B. tuned it, my Walther LGV was a “buzzard.”
I would like to distinguish between three options from my humble experience so far:
1. no dieseling smell and no smoke – never measured any strange V0 variation
2. dieseling smell – measured higher V0 when suddenly occured on one 12J springer, V0 was stable though. One issue is that after a longer brake the V0 will be initially different, then stabilized after 30 shots. It is not constant during one shooting session.
3. dieseling smell and smoke – so far 2 examples of pretty variable V0.
Perhaps each a bit stronger springer is dieseling in some way. The experiment you mentioned shows that actually. If there is a stable V0 – no problem for me. What I do not like is the dieseling smell (hate it) and smoke each shot is no-go for me. I just don’t feel the equipment is OK when it is smoking. It is possible that even smoking airgun will have a stable V0 – then you need to decide if you like it or not. So far I had these two examples of weak accuracy due to dieseling. So I try to avoid it.
RidgeRunner December 15, 2021 at 5:38 am
Hahahha great 😀 I was also thinking about it 😀
To be honest I do sometimes terrible mistakes. I do not use any translator. English is my 3rd langauge I use, unfortunately it is the weakest one. I’m sorry for my mistakes in advance! They will happen sometimes 🙂 But it might be funny 🙂 I already did one – I meant “seal” and wrote “sealing”. It is because in german it is “Die Dichtung” and everything with “-ung” has some brain connection to “-ing” 🙂 No problem with my mother-language which is polish, it would be “uszczelka”. Hahaha.
FM’s takeaway from this discussion is: if there is going to be any smoking, let your airgun do it and the rest of you stay away from the “lung torpedoes.” Good writeup on the subject, B.B.; it helps reduce FM’s anxiety level regarding the effects of dieseling on one’s airgun. It is clear that when it comes to lubrication, less is better; believe shootski made that point.
tomek do not be self-conscious about your English – you are making the effort to communicate and the meaning comes across. FM is a native Spanish-speaker who learned English in school and perfected it in the USA to the point his English is now better than the Spanish. Also picked up some German in the pursuit of my vintage automotive hobby and somehow managed to communicate with some of the parts vendors in Europe with not too much difficulty. No doubt the grammar and sentence construction is not what it should be. But, when you make the effort to communicate in the other party’s language, doors open for you. Who knows, may have to try and learn a little Polish and even Czech since some of the vendors who supply my hobby are now mostly in E Europe. FM’s head may finally explode in the process of doing that, so we would then have “brain detonation.” 🙂
FM – thanks! 🙂
I believe you mean JSB as example 🙂 of Czech vendor.
To be honest learning Polish is same difficult as learning Japanese. I tried as I was over one month working in Japan send from my company. So I could get this feeling.
My issue is that I use mostly some specific technical wording, not very often I have a chance for a normal “small talk” or just a non technical conversation. This is where you can see the difference in grammar and generally the sentence construction. I came to Germany when I was 22yo and then started to learn German langauge. Now I have to sometimes translate in my head Ger-Pol-Eng to get to the point in some cases 🙂
I found some interesting link, it is some guy from Russia, you can easily translate the page:
He showed the effect of dieseling a bit. Burned seals, destroyed parts and broken springs. Nice collection 🙂
English is my second language and American is my third.
Your English is fine. Now we will work with you on your American dialect.
Shootski – gladly. I’ve only been to the United States once, near Detroit. Also a business trip, unfortunately very short. I love this American way of pronouncing words 🙂 Nobody else is able to do this.
Same here FM, my first language was Spanish, my second English and my third French (which is essentially lost by now).
Hopefully my accent, while still there, is not too obvious when writing . . .
True story, GF1. During my years with Social Security, we collected stories about the colorful ways some of the clientele described ailments, disabilities and what-nots during interviews. My favorite was the one about the lady who came in seeking widow’s benefits because her husband had passed away suddenly and unexpectedly. When asked what was the cause of death, she replied “Oh, he died of a massive internal fart!”
To this day FM has a mental picture of the poor guy splattered on a wall jigsaw-puzzle like…gruesome, yet funny. Well, FM thought it was funny.
Right now Gunfun1 is trying (not) to picture that. 🙂
“Now you talk among yourselves and we’ll all get smarter.”
…Now there is a real leap in faith LOL!
Love this kinda blog! Thing is that it raises as many questions as it gives answers 🙂
As part of the “care and feeding” of my springers I’m in the habit of checking the screws and adding a drop of oil (through the transfer port) every half-tin of pellets or so. Guess that I’m fuelling the rifle as much as lubricating it.
That makes sense with my lower power springers that get a mineral oil/STP mix but my FWB 124 only gets silicon chamber oil. Is the silicon oil burning off as well?
The Cardews experiment is interesting but I wonder if (at a molecular level) if nitrogen compresses differently than air and that affected the velocities.
Hey Hank I thought about writing all this out but the LINK https://www.engineeringtoolbox.com/air-composition-d_212.html
does it way better than I could.
Shooting pure and dry Nitrogen slows down PPC is what I know from experience. If you want FAST, SAFELY, then Helium is the only game in town over plain old DRY air.
PS: take a look at the rest of this sites information on the most important gas we Airguners make use of.
Good common sense explanation of why you continued shooting detonations.
Your reference to the Cardew’s book prompted me to place an order for one. Already have their The Airgun from Trigger to Target book.
Welcome to new commentor tomek.
Decksniper – thank you! I was pretty long time a quiet reader 🙂 As I’m really back on the track with this hobby again I just can’t stay quiet anymore.
Today’s blog is fascinating to me, but it is so “densely packed” I will have to reread it more than once! :^)
I usually observe a whisp of smoke rising sluggishly from the muzzle after I shoot a spring air gun, but I used to assume it was residual vapor from the compression of the piston. But once I thought to sniff the smoke, I smelled burning oil, so I then concluded it was indeed smoke.
A groaner inspired by the chemistry discussed today: Oxygen, Hydrogen and Nitrogen walked into a bar. The bartender put up his hands and said, “Sorry guys, but we don’t serve elements here.”
Nitrogen just shrugged its shoulders, but Oxygen and Hydrogen blew up.
I must have needed that because I laughed out loud! That’s LOL for the millenials. 😉
Gotta remember that one! It’s right there with the one about the two peanuts who walked into a bar – one was a salted…
And why wouldn’t they. 😉
Reminds of something my buddy I use to drag race with would say to people talking about nitrous on cars. Basically a example to kind of visualize what happens when the nitrous gets to the combustion chamber.
The nitrous mixed with the fuel goes in the size of a golf ball and when the ignition happens the golf ball turns into a basket ball when it explodes from the ignition. Imagine what power that makes in that combustion chamber. Compression ratio sky rockets. Imagine all the extra force that’s being put to the engine components. Take that cylinder and how many rpms the engine revs times the cylinders of the engine. That’s a whole lot of energy happening for a lot of times.
Detonation…. not good.
Dieseling…. not good either. Why? What is right around the corner from Dieseling?
So how much nitrous do you put to a engine before it says boom? Regardless if you got the fuel mixture right for the amount of nitrous your adding. There is a limit to everything.
I might remember the details incorrectly, but back in the late 1970s my cousin attended diesel school. He told me (but he might have been putting his younger cousin on) that sometimes with an old, near-useless engine, they would take it out in the middle of nowhere, put crushed mothballs (naphthalene?) in the fuel, and run it until it went BOOM. They were pretty wild, so I always figured it might have been true.
Got to say they was right. I think I remember 😉 some moth balls getting dropped down some gas tanks on race night back in the muscle car days. And that’s when you could get 110 octane out of the gas pumps at the local Sunoco stations. Yep those old muscle cars did run. 🙂
Thanks BB, I have learned allot happens in the last .10 to .0010 of an inch, or centimeter depending on your particular dialect. Why do springers let their pistons bounce?
Wouldn’t a piston that locks at the end of its stroke be better, or would it just blow up with a detonation? Maybe the bouncing is a good thing. Maybe hydrogen is really a metal in a differant phase state. Hydrogen metal would be lite and abundant, unlike unobtanium is here on earth. Somebody should put a drop of distilled water in their transfer port, someone with a chronometer.
So, spring piston air guns are firearms in their own small way. Hmmm. Strange to think about.
This type of blog makes you go Hmmmmm….
So to the pcp guys that lube their pellets with various types of lubes.
Do you ever get a whisp of smoke from your barrel?
(I shoot pcp, but don’t lube my pellets.)
And if you use pure nitrogen as a fill gas, (I have a friend that uses a 6k nitrogen tank as his fill source I will ask him this too.) do you get a lower velocity than if you use plain air? Whether your pellets are lubed or not..
No on PCP whisps of smoke with lubricated pellets or bullets; but accuracy goes out the window with use.
Nitrogen (N2) molecules at 300 picometers are 2.6% larger than Oxygen (O2) which is 292 picometers. There are more fundamental issues that come into play at high pressures that add to just the size and Mass problems.
Nitrogen goes a lot slower than air at the same pressure.
PS: On Big Bores you can get condensation rings/clouds because of the pressure wave that forms with the right atmospheric conditions.
No never smoke. But definitely a mist at the muzzle. I put several drops of 3 and 1 oil down my barrel on my pcp’s to clean or whatever it does to the barrel to tighten my groups back up if accuracy starts going away.
Hmm. Imagine that.
You got me thinking about a craze awhile back where people on U-tube would smear a little petroleum jelly in the skirt of a pellet and shoot it from a springer. At the time we made fun of them, surmised it was probably dangerous and probably bad for the air gun. But now I wonder.
I have an off-topic question for the Dark Siders. Is it possible to use a PCP hand pump (no doubt with one or two adapters) to add air to a car tire that needs a bit more?
Thanks in advance,
However, because of the TINY pump bore it would take FOREVER!
Thank you! I learned at least one thing today:
If the adiabatic temperature (heat caused by compression and not long-lasting) remains high enough, this vapor instantly ignites, causing a diesel that’s no different from the one in Rudolph Diesel’s engine.”
I had never read (and remembered) or thought of that little detail being the case.
Once again, Thank You!
Dieseling is only normal in older airguns with leather piston seals which need to be oiled to enable them to seal.
In more modern guns with synthetic seals there should be no dieseling effect and no need to lubricate the seal or compression chamber
Heavens! Another airgun blog? One blog is enough for me. I hardly have the time to keep up with this one. It took me a long time to finally get up to BB’s 500th blog post. Maybe after I get caught all the way up, I will have time to read a second one.
You know what is typically said about free advice….
I didn’t see any real science in the Great Cardews Rebutal but it does call for a new Nitrogen test with a modern seals toting airgun.
I will say that i witnessed something very interesting that relates in a satellite vacuum test. They put the golden ball in the chamber and started to draw the vacuum. The day shift of Rocket Scientists/Engineers returned the following day to a failed vacuum test. They inspected the vehicle and chamber and tried again…yup! Next day another failed test…and another…and one more! Finally the piece of masking tape was found on the emergency relief handle inside the chamber! Outgassing from a 4″ or so long piece of masking tape caused the vacuum test failures.
That is the same thing that B.B. pointed out was the cause of a Diesel but because of the retained heat it then detonates because their is still some serious pressure in the Sproingers Compression Chamber and NOT the barrel.
This obviously calls for through experiment(s) to replicate the Cardews finding by a modern airgunner (God Father of Airguners) using a modern seal spring piston airgun and a calibrated Chronograph all paid for by PA!.
Hopefully the person who found the masking tape got at least an ‘At-A-Boy’. Nice find.
Speaking of using a modern seal in a piston air gun……why not use the same kind of material that is used as ‘piston rings’ in a YH second stage piston? That environment is sure a tough one to endure how temps and pressure, much like a sproinger does.
Not if the individual who “found” had used the tape to put up the PM tag.
I have read some reports that the YH compressors had ignition events in that stage. Don’t know much more about that compressor family…Gunfun1 does I believe!
Ironic that I experienced the first detonation today I’ve had in years.. After 20-30 shots I decided to put a thin layer of Moly on the barrel locking lug of my Stoeger ATAC. I was careful to avoid getting any of it in places it didn’t belong. Despite that the next shot was a detonation that sounded like a .22 Long Rifle shot from a pistol. No problems afterwards. Some Moly got in the bore or was it fumes?
It does sound like the Moly found its way to a place it wasn’t supposed to go, akin to water/moisture.
I never thought about using Moly but many thanks for saving me the ‘experiment’.
Thinking out of the box…….why not use a Portable Oxygen Concentrator on the intake of a compressor?
One could blend in a mix of richer oxygen in any air rifle, particularly a PCP?
Or is this ‘thinking’ too far ‘out of the box’ to make it practical?
Stay away from Oxygen enhancement for SAFETY!
Helium is the way to go if you want to shoot light small molecule. LEAKS and permeability are the bain of He as a PCP driving gas.
If safety is the prime motive/concern from staying away from Oxygen enhancement, then why not stay away from any and all things that aren’t ‘safe’?
Particularly, anything that might cause you to “Shoot Your Eye Out”.
I think you get my drift.
Even if they reach a higher pressure, PCP has no problem with diesel, because there is no such temperature increase as in the spring system. This is something I learned recently when I bought my first PCP and tried things a bit.
I’d like to share my “trick number 17” on how to add some silicone oil to the compression chamber and avoid a big diesel problem. I tried to shot with 0% oil on the seal. It is not good, the seal will suffer quickly and it does not guarantee a very stable V0. Sometimes it is just necessary to refresh the oil film in the compression chamber. Nobody would like to disassemble the entire system for this. It is not so easy to apply a very small amount of oil and distribute it well throughout the entire compression chamber area. I’ve tried many things and finally found something useful.
I take the small 2ml syringe with the needle (unsharpened). I take about 0.3ml of pharmacy gasoline (you know this very pure gasoline that you can buy in a small bottle, it is also called extraction gasoline, unfortunately I do not know the American nomenclature) and a few drops of silicone oil. It mixes up. Then I just cock the spring air gun and inject it through the transfer port into the compression chamber. Then do cock / release the airgun to evaporate the gasoline (takes 20 up to 40 times and you can’t smell gasoline anymore). The oil will remain and spread out as a thin layer. You can directly feel how it runs smooth. Then after gasoline is gone only the first few shots can be a bit smoky. Each spring-piston system has been working very well again for a long time after action described above. Please do not shot directly when the gasoline is still in the compression chamber 🙂
Personally, I don’t think this is such a good idea. Despite the care YOU take in the process you describe, you may give folks the idea of shooting gas out of their spring guns and having damage and injuries result. One slip of the hand off the cocking lever or barrel and you can have an explosion.
B.B. has described putting a drop or two of silicone chamber oil down the transfer port and standing the gun up for several hours. The oil is thin enough to work its way around the edge of the seal and the first few shots should distribute the oil along the sides of the chamber. The oil has a high enough flash point that it should not cause any dieseling. In a modern gun, this should suffice for 6 months to a year or as many shots as the manufacturer recommends. That’s simpler and safer than putting gasoline in the transfer port and then working the action.
I understand your point. Nevertheless I think when we are shoting airguns we should have this minimum “sense of safety” anyway. This is not the activity for stupid people. That’s why I’m not afraid to talk about it.
Never tried method like BB described. May be I’m just too impatient 🙂