New rifle detonation vs dieseling

[subscriber]

I hope some of you find this thread both entertaining and informative.  Here, the secret life of machines video series examines  the energy released inside internal combustion engines; petrol and diesel:

Petrol compared to black powder: 


Compression ignition principle:



Rewind the second video to see the rest of whole program from this amusing series.

[R.K.]

I know I shouldn't but ,somewhere I read that a new springer or NP rifle should be dry fired a couple times to remove excess lube and to "set" the piston seal.  Don't remember where I read it.Please correct me if I'm wrong! This ought to be good.

[subscriber]

I know I shouldn't but ,somewhere I read that a new springer or NP rifle should be dry fired a couple times to remove excess lube and to "set" the piston seal.  Don't remember where I read it.Please correct me if I'm wrong! This ought to be good.

Actually, Richard, the Beeman P1 / HW45 has a teflon piston seal that is seated by try firing it a few times.  That forces into a shape close to the cylinder it runs in, and ensures a good seal.  Quite likely that some other airguns manufacturers use the same "hammer forming" process.  Depends on the seal type, I think.

The Slavia 634 (new old stock) I got recently states something in the user manual about blowing the oil out of the barrel via dry firing.  I assumed that was a typo, as elsewhere it states not to dry fire it...

The barrel looked shiny and pretty dry when I got it; to the point of making me wonder if someone had perhaps already shot with this particular gun.  I have another new (old stock) Slavia on the way, and will see if it arrives full of oil.

My way of cleaning the barrel on a new airgun, is to saturate a cleaning pellet with thin oil, load it; then load a wadcutter behind it and shoot them through together (never just a cleaning pellet).   If I think it necessary, I will repeat this a few times; then go straight to just lead pellets, without drying the bore. Everyone has their own way of doing cleaning their guns; and that is all good.

I don't care if there is a little smoke initially when switching over to "dry" pellets.  What I can tell you, is that if you fill the rear of the pellet skirt with a drop of the same oil, it will diesel so energetically that the pellet goes supersonic.  When the oil is partitioned off in front of the pellet the discharge sounds just like with a dry lead pellet. 

The fact that trace oil clings to the bore afterwards is a good thing in my opinion, rather than something that should be avoided at all costs:  Such trace oil and the manner of placing it there, is how I prepare my airguns for storage at the end of a session; unless I know I will shoot some more the same day.  I simply never want to see rust in the barrel, and my method of oiling the bore works without dragging a cleaning rod through it.

If I had need to shoot critters on an opportunistic basis, then each shot taken with trace oil in the barrel would probably have a first shot or three deviation from the normal POI; so I understand why some people never pull oily patches through their barrels (only dry ones, to remove lead "lumps"; not all traces of lead).  For them, it takes too many shots to re-stabilize the point of impact.  I don't mind if the first 5 shots land a little off.  The paper rat targets I might shoot never move, even when I miss a perfect head-shot...

[Eddie_E]

Sorry if some of us use the terms diesel and detonation in a manner the is not scientifically accurate, but it's easier to explain to a new airgun shooter. To me a little whiff of smoke from cosmoline burning off the rifling and an extra 50 fps is one thing and a loud crack that is louder than a CCI Stinger at 2000 fps, where I'm surprised that I don't have pieces of the spring in my forehead is the other. Calling them the same might be scientifically accurate, but I think we need to discourage the latter.

[subscriber]

Sorry if some of us use the terms diesel and detonation in a manner the is not scientifically accurate, but it's easier to explain to a new airgun shooter. To me a little whiff of smoke from cosmoline burning off the rifling and an extra 50 fps is one thing and a loud crack that is louder than a CCI Stinger at 2000 fps, where I'm surprised that I don't have pieces of the spring in my forehead is the other. Calling them the same might be scientifically accurate, but I think we need to discourage the latter.

I think if the air rifle comes apart in your hands, calling it detonation is perfectly appropriate

I honestly believe that oil in the barrel burning off is not as serious as the same oil layer in the compression chamber igniting, for these reasons:

The amount of oil that can cling to the barrel wall is limited by its tiny circumference; VS the very large space between piston and compression chamber.

The transfer port will limit the flow of air in the event the pressure suddenly rises due to a significant combustion event.  With combustion in the barrel, the TP acts as a restrictor that creates a pressure drop and limits back-flow, thus shielding the piston somewhat from the pressure spike in the barrel.  If a large combustion event occurs in the compression chamber, then TP flow restriction acts to make the event in the compression chamber harder on the piston and spring.

The barrel wall is way stronger than any pressure you can generate via compression ignition by means of a lead pellet as a plug  (Glue the pellet in place and all bets are off ).  The compression cylinder has a much larger diameter and a thinner wall, hence it is much more fragile than the barrel to over-pressure.  Even then, the compression chamber has a "blow-off" safety valve protecting it, in the form of the piston and mainspring. 

The O-ring at the breech on break barrel is likely going to leak and act as anther release valve.  Of course, this is not good for the O-ring; if repeated many times.

Thus, the idea that you could disintegrate a spring air rifle by dieseling oil seems absurd.  Perhaps if you filled it with a stoichiometric mixture of nitromethane and pure oxygen, you might break the spring, bulge the compression tube and split the stock.

Consider the pressure event that results from the piston slamming into the air column at the front of the cylinder in normal operation.  That resulted from the piston running all the way from the rear of the compression cylinder after de-latching from the sear.  If a dieseling event does not manage to push the piston all the way to the rear of the piston stroke, just how much energy did that event have, compared to the energy normally released by the spring? 

Peak gas pressure is another consideration and an important one, but short of bulging the compression tube (or blowing the end off), it is really the spring, piston seal and breech O-ring that suffer from heavy dieseling.

Injecting several drops of CLP into the transfer port of a spring air rifle is definitely contraindicated, and new airgun owners should be warned about proper lubricants and how to apply them.  CLP's light hydrocarbon detergent content makes it even easier to ignite than pure mineral oil, or diesel.  So, rather than preserving your airgun by lubing the piston with whatever oil you happen to have, you may be damaging it.  Certainly, a number of heavy diesel events, or frequent ones that increase the report, may drastically reduce the life of the spring and burn the piston seal.  This is the opposite of making choices to increase the life of your new air rifle. 

Burning off the two drops of oil that adhere to the surface of a new barrel don't qualify as abuse in this regard.  In addition to the reasons why in-barrel combustion are not "as bad", the fact that the first two pellets will squeegee out the bulk of this oil without burning it, is the other reason.

I shoot firearms with trace oil in the barrel based on these criteria:

Is the oil just enough to make the barrel shiny; or does it obscure the rifling, or pool at the bottom?  If the latter, patch it out before shooting; else blast away.

If it is a bottle neck case centerfire rifle and the situation is not an emergency, then patch the chamber wall dry and check the bore for any obstruction before shooting.

Most handgun calibers get shot directly with trace oil still in the chamber and barrel.  There are exceptions where the lack of case grip due to oil causes case head flow, causing sluggish cylinder rotation, such as .44 Mag. 

Service pistols with "carbon steel" barrels carried in holsters a lot and shot very little should have trace oil in the barrel.  Else they will rust.  Rust impedes projectile travel a lot more than a little thin oil...

[Bryan Heimann]

I, too, seriously doubt you could break a quality spring gun with a few drops of oil. 

But if you do it a few times, I can tell you for certain it will break the spring.  As sure as heavy pellets can break a spring, deiseling it will break it so much faster. 

And it has been documented, deiseling a springer could possibly re-cock the gun if it is violent enough, something to keep in mind.  That is alot of force.

Not to mention, pellets blown down the bore without their skirts, leaving the barrel plugged, and etc. 

It is certainly not a big deal, a little bit of deiseling in a new rifle.  But it can do a lot of damage if you make it a habit.

Depending on the chemical you choose, it certainly could do serious damage.  Weihrauch tried to build a rifle built for deiseling with ether, didn't work out because the piston seal couldn't hold up to it.  That, and it was too erratic.

[subscriber]

But if you do it a few times, I can tell you for certain it will break the spring.  As sure as heavy pellets can break a spring, deiseling it will break it so much faster. 

Absolutely right.  People worry about shooting heavy pellets reducing spring life (when that is their most accurate pellet).  Frequent heavy dieseling will be very hard on the spring; and break it in short order.

And it has been documented, deiseling a springer could possibly re-cock the gun if it is violent enough, something to keep in mind.  That is alot of force.

A lot of force, but no more than you apply when you cock it.  So, not really that much; except if the piston slams into the endcap, as if it were compressing a spring twice as long.

Certainly, if your spring air rifle recocks itself, stop what you are doing and call a professional...

[Bryan Heimann]

But if you do it a few times, I can tell you for certain it will break the spring.  As sure as heavy pellets can break a spring, deiseling it will break it so much faster. 

Absolutely right.  People worry about shooting heavy pellets reducing spring life (when that is their most accurate pellet).  Frequent heavy dieseling will be very hard on the spring; and break it in short order.

And it has been documented, deiseling a springer could possibly re-cock the gun if it is violent enough, something to keep in mind.  That is alot of force.

A lot of force, but no more than you apply when you cock it.  So, not really that much; except if the piston slams into the endcap, as if it were compressing a spring twice as long.

Certainly, if your spring air rifle recocks itself, stop what you are doing and call a professional...

But consider the violent change in direction to re cock the gun.  That spring just went from coming freely uncoiled, to be snapped back to nearly coil bound, in an instant.  That is a whole lot more force that what it recieves in a cocking stroke.  If you tried to re cock it as soon as you pulled the trigger, it would for certain damage the cocking shoe, tip of the cocking arm, whatever it connects to the piston with.  Liable to shear it off completely. 

That much force, can do a whole lot of damage!

[subscriber]

But consider the violent change in direction to re cock the gun.  That spring just went from coming freely uncoiled, to be snapped back to nearly coil bound, in an instant.  That is a whole lot more force that what it recieves in a cocking stroke.

Yes.  Bad for the spring.  Very bad.

The rest of your statement about recocking the gun just after it fires being hard on the cocking shoe is not relevant, as those components are not involved in dieseling.

[Bryan Heimann]

But consider the violent change in direction to re cock the gun.  That spring just went from coming freely uncoiled, to be snapped back to nearly coil bound, in an instant.  That is a whole lot more force that what it recieves in a cocking stroke.

Yes.  Bad for the spring.  Very bad.

The rest of your statement about recocking the gun just after it fires being hard on the cocking shoe is not relevant, as those components are not involved in dieseling.

Maybe you should think it through before posting such a hasty reply.

I never implied the cocking shoe would be damaged by deiseling.

You posted that the pressure that occurred When a gun was recocked after deiseling was no more than when you cock it by hand.

Well?  It is actually a WHOLE LOT MORE than when you cock it by hand.

Possibly enough to even bulge the tube.  Might even create enough pressure to bulge the tube without cocking it!

Unless you can cock the gun faster than it can complete a shot cycle, you will never apply marginally the same amount of force as would be generated under those circumstances.

[Bryan Heimann]

But, I guess I should depart from the thread. 

No waffles being served here, only logic.

Thanks, and you're welcome.

[subscriber]

You posted that the pressure that occurred When a gun was recocked after deiseling was no more than when you cock it by hand.

Well?  It is actually a WHOLE LOT MORE than when you cock it by hand.

What I said is quoted below.  I compared the energy seen in recocking; then went to state that the pressure was another matter.  So, you are getting ahead of yourself with your speed reading.

Consider the pressure event that results from the piston slamming into the air column at the front of the cylinder in normal operation.  That resulted from the piston running all the way from the rear of the compression cylinder after de-latching from the sear.  If a dieseling event does not manage to push the piston all the way to the rear of the piston stroke, just how much energy did that event have, compared to the energy normally released by the spring? 

Peak gas pressure is another consideration and an important one, but short of bulging the compression tube (or blowing the end off), it is really the spring, piston seal and breech O-ring that suffer from heavy dieseling.

[Bryan Heimann]

You posted that the pressure that occurred When a gun was recocked after deiseling was no more than when you cock it by hand.

Well?  It is actually a WHOLE LOT MORE than when you cock it by hand.

What I said is quoted below.  I compared the energy seen in recocking; then went to state that the pressure was another matter.  So, you are getting ahead of yourself with your speed reading.

Consider the pressure event that results from the piston slamming into the air column at the front of the cylinder in normal operation.  That resulted from the piston running all the way from the rear of the compression cylinder after de-latching from the sear.  If a dieseling event does not manage to push the piston all the way to the rear of the piston stroke, just how much energy did that event have, compared to the energy normally released by the spring? 

Peak gas pressure is another consideration and an important one, but short of bulging the compression tube (or blowing the end off), it is really the spring, piston seal and breech O-ring that suffer from heavy dieseling.

Energy in a gun that deiseled so hard, it recocked itself, still far greater than when you cock it.  Think about the velocity of the piston reversed hard enough to recock it, how fast it must return.

You want to catch me up on verbiage, or even to continue this with me at all, we can do it in private messages.  I'm done with you, and this thread.

[subscriber]

Energy in a gun that deiseled so hard, it recocked itself, still far greater than when you cock it.  Think about the velocity of the piston reversed hard enough to recock it, how fast it must return.

The bold portion is true, but only if the piston slammed into the back end of the compression tube (as made clear in my earlier post).

This is like throwing a bowling ball up in the air (with gravity instead of a spring, pushing it down).  If you can manage to ignore air resistance due to its insignificance; all of the ball's velocity is converted to height on the way up.  All of its height is converted to velocity on the way down.

No matter how large your peak force and peak acceleration when throwing that bowling ball upwards, the velocity at which it leaves your hand dictates how high it will go.  The height reached at the top of its travel dictates the ball's velocity on the down.   Just as if it were driven by a very large volume gas ram, with a near constant "spring rate".

Now, consider that you are throwing the bowling ball upwards in a room with a vaulted ceiling.  As long as the ball just kisses the ceiling on the way up, the energy you imparted is the same as the energy the ball has on the way down.  It matters not if you used 160 lb applied over one foot, or 80 lb over two feet to launch it.  It is only if the ball slams into the ceiling that "extra energy" can damage anything.

What damages the spring in a dieseling airgun is not the fact that the piston is driven backwards, but making the spring coils clash into themselves violently.  So it is acceleration and jerk, driven by gas pressure that does the damage, rather than too much energy.  Even if the piston never comes close to traveling far enough to recock.

We suffer from the flip-sides of the same disease:  You want to prove me wrong.  I want to prove me right.  What is amusing, is that we agree in principle about all the important details,  But, you need to have the last word.  So, go for it. I am done with this thread; unless someone says something sensible that has not been said before.

[subscriber]

I would like to publicly apologize to Bryan H for having more sport with him than really necessary.

I just found his insomnia thread in the Backroom that made it clear to any thinking person, that such arguments are contraindicated.

[Mossonarock]

Good grief.

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

IKR......

I'm sure I had a screwed up expression on my face when I read that too.
Why... Eh, I'm not going to bother asking.... I know its pointless but I wish my opinion that its pointless was a waffle served up.

I agree that the term "detonation" ought to be dropped by the airgun community.

I also want to express my concerns with metal fatigue after my experience last night. What happened was... I broke a manual log splitter with nothing more than my own bones and muscle. Who'd a thunk a wirey guy like me could do that?

I'd say, if your airgun blew up in your face and blew to pieces, that was an explosion caused by extreme dieseling. Dieseling is when the vaporized lube particles actually combust whether just a wee poof or it blows your airgun up and sends shrapnel flying. If that's a waffle for you, then eat up!

[Bryan Heimann]

Hahahaha!  All I am saying is, I never saw a shockwave coming from a springer.  Or a firearm for that matter.

That's the difference.  A supersonic shockwave that moves ahead of the explosion, you can see it if you are far enough from it.  Detonations are extremely violent and fast.

I'm guilty of calling it detonation as well.  I agree we gotta stop using that terminology.  More like ignotion, or combustion???  Combustion I think is the correct term according to the Googles.  For sure it ain't detonation!