New rifle detonation vs dieseling

[Mossonarock]

I've had a Hatsan Dominator with a metal "spring" and just today received a Hatson Dominator with a gas piston "vortex". Both in .25 cal.
I wanted to compare the two rifles in all respects.


So, as soon as I got the Dominator Vortex, I chrony tested it. The first couple shots were about 915 fps with Barracuda Green 19.91gr. My jaw hit the floor. I was not expecting to see that. However, each shot was slower and by the tenth shot or so the fps was down to 815fps. Unfortunately, for some reason my chrony was only registering every third shot or so. hhmpf.


What I am wondering if the initial high fps was from an extra push provided by detonation of the factory lubes and as it burned off the fps dropped or what? Any ideas? The smoke coming out of the barrel was quite dense.

[Doug Wall]

If the gun sounds like a .22lr going off, it's dieseling (detonating). There can also be some combustion going on without the detonation. The smoke is another indication. That usually goes away after a few shots, and the gun will continue to "settle/break in" over the next few hundred shots.

[Novagun]

Dieseling is accompanied by an increase in velocity and detonation by a decrease although detonation is a a more violent occurence. All depends on the fuel available.
There was a thread just recently that detailed the two events that explained it well.

[Nathan]

When I get a new spring or gas ram gun (new or refurb) or a spring/gas ram gun I've tuned and lubed myself I never do the first few break in shots with lite for caliber pellets. And I never use lite for caliber alloy pellets either for break in. I always shoot the first few shots with mid to heavy weight for caliber lead pellets. Your opinion and experience may be different.

Nathan

[jab]

yep   thats what is happening,  just got a new one today.  it's still smok'n after  maybe 20+ shots.  first shot sounded like  a BB cannon,  had to wait for the smoke to clear,  so I could see to reload.    Kinda like shooting a chinese Black powder gun

[Bryan Heimann]

Yes, 919 fps in a box stock .25 cal springer is, for sure, dieseling.

Detonation is what explosives do.  It's dieseling, or burning.  Even gunpowder burns.  Burns all the way down the barrel.  Detonation?  That's explosives.  The airgun world is confused on this.

Don't fret or sweat, most new springers dielsel a bit.  Clean the barrel very well.  Shoukd help calm it down a bit and enhance accuracy.  Then get back to us after 20-30 rounds downrange, after a good barrel cleaning, and a few groups.

[Dockey 454]

There can also be some combustion going on without the detonation. The smoke is another indication.

I have had this "issue" since i bought my fire NP. Every single shot causes smoke in the barrel, even a year and thousands of pellets shot....

Anything else that can cause smoke?

This to me would indicate there is to much lube in the gun, and it's getting past the seal. I've had a few new guns that had to be cleaned up, and lubed the right way. Not to mention some nicked seals from the factory.
  Tom

[Bryan Heimann]

About smoke- if it is accurate, don't worry about the smoke.

[Mole2017]

...Every single shot causes smoke in the barrel, even a year and thousands of pellets shot....

Ah memories...Does it smell like a candle that had just been put out?

I bought my CFX refurbished. Every now and then I'd get a cracking shot. ("Ooops! Was that me?"...and look around for witnesses.) I forget how many shots I put through it before those stopped, but it was way more than 200. I got smoke a lot early on, but that would happen off and on for a longer while.

No smoke these days, but I can still smell the candles
One of these days I'll replace the seal and try to lube it right.

[Mossonarock]

I've cleaned out the compression chamber and all that. Relubed it. No more smoke now.
The fps settled down to about 700 with the Barracuda Greens.

Yeah. In my opinion, dieseling vs detonation is kinda like six of one or half a dozen of the other.
Either way, lubes combust whether its an explosion or smolder.

[subscriber]

There is much dogma expressed about dieseling; even when it is patently wrong:

1. "To stop a new spring airgun from dieseling, use a heavier pellet". 
2. "if it cracks like a .22 rimfire it is dieseling".  Thus; "if it stops cracking like a rimfire, it is no longer dieseling."

Obviously, belief #1 stems from #2:

Heavier pellets raise the peak pressure in spring airguns, thus more readily generating air temperatures high enough to ignite any lubricant mist that may be present.  Therefore, heavy pellets (for the caliber) are more likely to diesel than light ones. 

The above dogma about using heavy pellets to suppress dieseling stems from the fact that heavy pellets are less likely to be travelling over 1100 FPS (or whatever the speed of sound is at your location), even when dieseling is involved.  Thus heavy pellets will induce significant dieseling more often than light pellets.
 Yet, they won't announce with the sharp crack that lighter pellets often produce when dieseling occurs with them.

Just like with an engine, if your airgun runs rough, stop to consider what you can do to smooth out its operation. 

If a spring airgun smokes, it is burning something, probably lubricant.  That oil or grease is being lit via compression ignition; AKA dieseling.  Unless your airgun is extremely loud and jolts unusually in your hands, it is not going to self destruct.  So, the idea that your airgun could be dieseling without you knowing, and thus secretly destroying itself is rather ridiculous. 

Early spring airguns had leather piston seals that had to be generously oiled, or they would leak air.  That meant oil was always present in the compression chamber (oh the horror).  Such airguns burnt oil at a slow but steady rate, and were quite accurate; despite their continuous "secret dieseling"...

What some call detonation, is just heavy dieseling.  It is so severe that the airgun is "protesting" by means of obviously loud sounds and heavy vibration.  Not unlike when someone lugs an old gas engine, running on too low octane fuel to the point of making it sound like a diesel.  It is really saying, "if you want me to last, don't do that to me". 

Heavy dieseling is likely to raise the projectile velocity by hundreds of feet per second.  It is likely to vary from on shot to the next by over 50 FPS.  The dispersion this causes on target should be reason enough to find a permanent "fix" or at least a mitigating factor (like using a different pellet).

For the deniers out there.  Those who would be grossly insulted by claims their spring airguns are dieseling, consider this:  Just because you don't see smoke bellow forth from the muzzle on every shot does not mean lubricant is not being burnt:  Break the barrel on your spring airgun and look through it against the light, directly after shooting each of 10 shots in quick succession.  That brown haze you see and can blow out, is smoke.  Smoke is partially burn hydrocarbons.  How do you suppose that got there...

Just because some airguns have an obvious haze hanging in the barrel after the shot does not mean they are in danger of disintegration. Or, in need of stripping down, degreasing and re-lubing. 

If a spring airgun has a shot to shot velocity difference of less than 25 FPS, and is sufficiently accurate at your intended range; who cares if it burns a little lube along the way?

Arguing about dieseling VS detonation; and that there is a fundamental difference, sounds political; and is about as useful.   Large abrupt releases of thermal pressure energy into a system not designed for it may lead to damage; especially if repeated many times.  Smaller and less abrupt releases of thermal pressure energy are not going to do much at all, even if they happen hundreds of times; except make you miss your shot.  Especially, if the events are inconsistent.

[Mossonarock]

"Arguing about dieseling VS detonation; and that there is a fundamental difference, sounds political; and is about as useful"
I agree hence my analogy to an explosion vs a smolder. You accurately described scenarios where an "explosion" would dramatically increase fps vs scenarios where a bit of lube may "smolder" a bit but not significantly increase fps. Either way some lube burned.

[Novagun]

Still just waffly opinions with no back up to them.
This information falls far short of that provided by T Domingo and others in a previous thread. They at least gave the apppearance of knowing what they were talking about and probably did.
Perhaps reading that and making some criticism of it would advance the topic.
A declaration of qualification to comment might add weight.

[Mossonarock]

"Waffly opnions"? You mean like this one?: "Dieseling is accompanied by an increase in velocity and detonation by a decrease although detonation is a a more violent occurence."

My qualifications? I understand how diesel engines work. Did you know that diesel fuel detonates/combusts in a diesel engine without sparkplugs? Anyone ever wonder how that happens? I also have a lot of experience with the requirements for fuel combustion in campstoves- alcohol, white gas, kerosene and even veg oil.

One thing I find missing in the discussions of detonation vs dieseling that I've come across is mention of lube "vaporization". When the air in the compression cylinder is compressed during the shooting cycle, the temperature of the air increases. That increase of temperature can "vaporize" some lube and it can do so without that lube combusting/dieseling/detonating. There's a lot of variables that go into play on how much so the lube vaporizes and whether or not it will diesel/detonate/etc. However, anytime that lube combusts/diesels/detonates/blah blah, it had to have vaporized first. Its just like in campstoves, fuel has to be vaporized first before it can be ignited. So, in campstoves, we have vaporizing tubes that the fuel goes through before the fuel is fed into the burner head. The trick in airguns is knowing when you merely have vaporization of lube or if that lube burned/dieseled/etc.

[Novagun]

Not my opinion. Relayed from those who seem to know. At least know more than I do.
Maybe they have some specific training. They write as if they do and refer to scientific papers.
I will try and find the thread.

[Novagun]

what is dieseling ?
« on: August 03, 2018, 04:20:37 PM »
Quote
I hear that term in here, and no clue what it means ?
Thanks

Here is the thread. My contribution was limited to trying to understand and describe the original question but including detonation.

[outdoorman]

One thing I find missing in the discussions of detonation vs dieseling that I've come across is mention of lube "vaporization". When the air in the compression cylinder is compressed during the shooting cycle, the temperature of the air increases. That increase of temperature can "vaporize" some lube and it can do so without that lube combusting/dieseling/detonating. There's a lot of variables that go into play on how much so the lube vaporizes and whether or not it will diesel/detonate/etc.

  This inconsistency is exactly why I completely degreased the compression chamber of my D34 and only use Krytox lubrication. It has zero flash point and cannot cause or contribute to combustion. My gun never diesel's. That variable has been eliminated.

[subscriber]

A declaration of qualification to comment might add weight.

Now that really sound political.     

Facts and logic trump appeals to authority; and real or claimed qualifications, every day of the week.

The textbook definition of detonation means an "explosion triggered by a shock wave, travelling through the medium at the speed of sound; where all the mass participating in the reaction is converted to gas nearly instantaneously". 

This, in contrast with a flame front moving through the medium from one end to the other, or from a point radiating outwards.  In deflagration, the medium is converted to gas only at the flame front; not everywhere at the same time.

The word "detonation" sounds "bad", but does not really tell you if it was a big bang; only that it was a short lived.

Detonation on a small scale might still be damaging, just like cavitation causes erosion of pump impellers:  Very small events, but intense enough to flake off surface material.  Especially when repeated so many times that it fatigues the material; even if only superficially.  Once, some material has flaked off, it exposes new material to the small shock events, so the erosion continues.

"Detonation" in a gasoline engine can damage bearing when heavy; and erode holes in piston crowns when light, but continuous.  With the latter, it flakes off the protective aluminum oxide layer, exposing the fresh aluminum to further oxidation; until there is a hole through the piston crown...

If your springer diesels or detonates so heavily that it recocks itself, you are not going to enjoy shooting it very much, or for very long...

[subscriber]

One thing I find missing in the discussions of detonation vs dieseling that I've come across is mention of lube "vaporization".

Wasn't this close enough for you?

Heavier pellets raise the peak pressure in spring airguns, thus more readily generating air temperatures high enough to ignite any lubricant mist that may be present.  Therefore, heavy pellets (for the caliber) are more likely to diesel than light ones. 

After all, the fuel in a diesel engine is just a fine mist after injection, yet it ignites.  True vaporization happens after the fuel mist temperature goes up from compression; and much more from the early combustion.  Thus the smaller the initial droplets, the easier they ignite; because it takes less energy to actually vaporize them.

What is the difference between mist and vapor?  Mostly particle size:  Mist droplets are composed of clusters of multiple molecules, while vapors (gases) are composed of single molecules of a given substance.

Hence, higher viscosity sticky grease is harder to whip up into a mist than a thin oil; which is why magnum springer compression chambers should never be lubed with regular oil...

[Bryan Heimann]

Good grief.

Since somebody is all in a a tizzy over my waffly comments...

Long story short, 900+ fps .25 cal at 19+ grains is a sign of a load of oil in the barrel and/or compression chamber, either brand new gun or a bad seal, or etc.

With the really light 14-16 grain .25 ammo, yeah I could see 900 fps a realistic achievement in a very powerful springer, without the "extra burning oil".


FYI cleaning a barrel really well before the first shot really cuts down the dieseling of a brand new springer.