Dieseling

[Michael M.]

My nitro piston Crosman Varmint was squeaking a little, so I added a single drop of silicone oil to the top of the piston.  Wiggled the barrel to work the oil in a little before shooting again.  The oil is labeled as high temp (to 500 degrees) but the rifle dieseled anyway.

Can anyone tell me how to lube the piston without the fireworks?

[avator]

I just posted my method in a different thread.

Here is a link.

https://www.gatewaytoairguns.org/GTA/index.php?topic=212627.msg156511158#msg156511158

[Roadworthy]

You will note from Bill's instructions is lubrication involves disassembly of the rifle.  If you're up to disassembly I have my own method.  It involves cleaning all the lube from the compression tube with a solvent - brake cleaner, acetone, whatever.  I rub molybdenum disulfide powder into the compression tube walls.  I'll then put a thin film of Krytox on the piston seal lip.  Check for ease of movement of the piston within the compression tube.  It should take three to five pounds of force to move the piston and lubricated seal.  If it's too tight I'll reduce the size of the seal, lubricate, and try again.  When I'm happy the piston and seal have the correct amount of resistance I'll reassemble.

[Michael M.]

Thanks for the help.  I do not have the compression equipment for disassembly.  The nitro assembly works fine but the piston would squeak a little during cocking.

I thought the high temp oil would be good but was surprised by the dieseling.  I guess the compression temps must be impressively high.

[Methuselah]

If it wasn't said, protect your piston seal from damage by the cocking slot during insertion, and sharp edges (debur the slot).

Gluing buttons on the piston is an option too since you will have it disassembled...

[nced]

My nitro piston Crosman Varmint was squeaking a little, so I added a single drop of silicone oil to the top of the piston.  Wiggled the barrel to work the oil in a little before shooting again.  The oil is labeled as high temp (to 500 degrees) but the rifle dieseled anyway.

Can anyone tell me how to lube the piston without the fireworks?

A couple personal opinion comments.......

"so I added a single drop of silicone oil to the top of the piston"
I never let any "silicone lubes" near the sliding steel surfaces of my HW springers. It's rather easy to prove that silicone lubes promote galling between steel sliding surfaces by chucking a steel rod in a lathe or drill press, then lube the rod with the "silicone lube of your choice". Next start the lathe or drill press and hold another steel rod against the one with lube using some pressure and see how quickly the galling starts. LOL, plain ole "wheel bearing grease" holds up longer without galling.

"labeled as high temp (to 500 degrees) but the rifle dieseled anyway."
https://www.fishersci.com/shop/products/silicone-oil-high-temperature-usable-temperature-range-25-250-c-open-system-25-315-c-closed-system-thermo-scientific/AA4589622
From the above attachment.........
"Silicone oil, high temperature, usable temperature range: 25 to 250°C (open system) and 25 to 315°C (closed system), Thermo Scientific Chemicals"
"Flash Point    >300°C (572°F)"
"Placing lube on the "top of the piston" (especially near the transfer port with high air temp and velocity) is the worse place, despite what was recommended in the old Beeman owners manual for guns like the older HW35 that had leather seals that needed to be oiled. Later the Beeman owner's manual cautioned that all lubing was to be done only at the Beeman facility.

https://www.pyramydair.com/airgun-resources/manuals/beeman-r-series-breakbarrel-air-rifle-owners-manual.pdf

From the above.........
Maintenance
In the unlikely event your rifle malfunctions or exhibits reduced performance, DO NOT attempt to fix the problem yourself.
1. Air compression chamber: The air compression chamber and piston seal require no lubrication. They should be lubricated during factory service only.

The way I did internal (including piston and piston seal) lubing of my HW springers when I used traditional molly paste was to first disassemble the guns, thoroughly clean and degrease of the old grease, then reapply a thin film of molly paste on the sliding surfaces <B>making sure to get NO lube on the face of the piston seal. Lube was only applied to the sides of the piston seal and skirt of the piston (again, only a film) because molly paste will also diesel since it has a petroleum base. Here is an example of fresh factory lube on the piston and spring of my HW95 straight from the box after disassembly and another example of a HW95 piston coated with "HW factory lube" from a "customer gun" (used to do tuning and maintenance) after a time of use..........


Several years ago I read where a piston gunner was using a Dupont "space station grease" that didn't diesel and it was so inert that it could be used for lubing the valves of oxygen tanks. The stuff was called Dupont Krytox so I found the stuff listed online and ordered a half ounce tube to test the claims.........

I slathered the stuff inside the R9 deliberately getting some of the piston seal, reassembled the gun and did a test shot over the chrony. LOL, no dieseling, grey smoke from the muzzle or POW with the shot!! I even had this amount of Krytox GPL205 left over for further testing......


After a few shots with the Krytox GPL205 I noticed a "strange whiff" after the shots so after 1000 shots I broke down the R9 for an inspection. Even though I had scrubbed out the R9 receiver with non-chlorinated brake cleaner and then wiping dry because there were warnings that inert Krytox doesn't combine with petroleum based grease. What I noticed was some black streaks in the white Krytox and was surprised so I again stripped the R9 internals and relubed with a thin film of Krytox and did another 1000 shot test. The "strange whiff" was still present however not as pronounced as before. After the second 1000 shot test an inspection revealed that there was still slight "grey in white" lube. Another strip and 1000 shot test and all was good with no further "strange whiffs" or "grey in the white".

These "black/grey on white lube" incidents had me puzzled so I further inspected my R9 receiver and found this.........

Even though the R9 was performing well with accuracy I noticed that the factory brazing between the receiver tube and barrel pivot fork was very porous internally. I don't know for sure but I suspect that the "strange whiffs and black in white" was simply molly paste from years of shooting was driven so deeply in the voids and "cooked" by temp and pressure that even soaking with brake cleaner didn't dissolve the krud however the Krytox was dissolving the old lube. The R9 is an older HW offering however I bought a brand new .177 HW95 a few years ago and noticed that the HW95 didn't diesel at all, even with the first shot. The "outta tha box" factory velocity was too high (CPL @ 880fps) after a few dozen "clearing shots" and a bore clean. I broke down and stripped the new gun for replacing the "dinosaur oil based lube" with the Krytox GPL205 and this is what the inside of the receiver looked like after pulling the piston. No porous braze...........


Anywhoo, lubing a springer is indeed a personal issue and tuners have been successfully using petroleun based molly bearing lubes for decades however I've been using the "Krytox stuff" for several years now with complete satisfaction. I use the GPL205 when grease is needed and GPL105 when oil is needed like the cocking lever rivet. My "Krytox stash".......

[Michael M.]

Thanks again for the info.  I don't have the compression tool needed for disassembly and thought the piston was needing some lube.  I guess I will just put up with the squeak.  I have lubed the pivot and latch with some 3-N-1 oil, after every full tin of pellets.

[nced]

Thanks again for the info.  I don't have the compression tool needed for disassembly and thought the piston was needing some lube.  I guess I will just put up with the squeak.  I have lubed the pivot and latch with some 3-N-1 oil, after every full tin of pellets.

I know little about Crosman piston guns but this video might help you with disassembly.

No "fancy" compressor needed, just a simple bar clamp to compress the gas ram for removal when relubing or replacing the piston seal.......


Funny thing is that I use a padded Groz sash clamp to compress the spring when disassembling/reassembling my HW break barrels...........

[Michael M.]

Thanks for the vid.  I didn't know that those clamps were so reasonably priced.  Guess I need to get one.

I have moly grease.  Would that be ok for everything behind the piston?

[nced]

Thanks for the vid.  I didn't know that those clamps were so reasonably priced.  Guess I need to get one.

I have moly grease.  Would that be ok for everything behind the piston?

Molly paste has been used successfully for decades with thin application BEHIND the piston seal. The main issues I had with molly paste was the fact that it will "be pumped" past the piston seal to diesel in the compression area, especially with excess. Also, I've found that over time the petroleum carrier will "outgas" and the lube will become a "goopy mess" and I've even worked on piston guns where the molly paste actually became "hard and cakey". Here is a pic of a tub of molly paste from an airgun supply shop that thickened in the sealed tub over a couple years to the point that the goop could support a socket head cap screw on the side of the tub with only a few partly embedded threads..................

Actually, reconstituting thick molly past is pretty easy by thinning with a bit of mineral oil, however mineral oil will also diesel.

[Back_Roads]

 This product works, and no tear down needed follow instructions to a T .
https://www.pyramydair.com/product/air-venturi-tune-in-a-tube-airgun-lubricant?a=7927

[Michael M.]

Thanks James.  I will order some.

Clicked the link about the crossbow.  That thing looks tedious and clumsy.

[nced]

Thanks James.  I will order some.

Clicked the link about the crossbow.  That thing looks tedious and clumsy.

It might be good to read this thread............
https://www.gatewaytoairguns.org/GTA/index.php?topic=191953.0

My experience with "goop on the spring" to kill twang and vibrations was less than satisfactory because the stuff I used (heavy tar shown in my posted pics) was initially good for killing "Beeman R9 twang" however the "fix" was temporary at best. The downside was that the "goop" made my guns' velocity dependent on the atmospheric temperature so accuracy was also affected. I don't know anything about the "tune in a tube" stuff so perhaps your mileage may vary. Still, if the "goop in a tube" does indeed make your gun "temperature sensitive" or the "dieseling" still stays the same or gets worse you'll be doing a proper disassembly internal stripping and re-lubing. The only thing I found that makes for a long term consistent shot cycle was installing a snug fitting spring guide along with proper lubing.

Still, if dieseling is your ONLY issue perhaps it's better to simply stop with the "excessive lube" and let the stuff "burn off" if the dieseling is only a bit of smoke from the muzzle after the shot. If the dieseling is an actual "detonation" evident by a crack when shot I PERSONALLY believe that a disassembly, stripping of the excess lube, then relubing sparingly with "springer appropriate lube".

[Methuselah]

This product works, and no tear down needed follow instructions to a T .
https://www.pyramydair.com/product/air-venturi-tune-in-a-tube-airgun-lubricant?a=7927

Any idea what's in it? I'm guessing there's a material safety data sheet on it...

[Novagun]

There is a previous thread that talks comprehensively about dieseling and detonation . One of the contributors was a scientist or well qualified person. I can-t find it yet but still looking .
It tells go exactly what happens and is worth knowing

[Sqwirl57]

This product works, and no tear down needed follow instructions to a T .
https://www.pyramydair.com/product/air-venturi-tune-in-a-tube-airgun-lubricant?a=7927

Any idea what's in it? I'm guessing there's a material safety data sheet on it...

I have been told it is essentially Almagard 3752

[Michael M.]

Thanks James.  I will order some.

Clicked the link about the crossbow.  That thing looks tedious and clumsy.

It might be good to read this thread............
https://www.gatewaytoairguns.org/GTA/index.php?topic=191953.0

My experience with "goop on the spring" to kill twang and vibrations was less than satisfactory because the stuff I used (heavy tar shown in my posted pics) was initially good for killing "Beeman R9 twang" however the "fix" was temporary at best. The downside was that the "goop" made my guns' velocity dependent on the atmospheric temperature so accuracy was also affected. I don't know anything about the "tune in a tube" stuff so perhaps your mileage may vary. Still, if the "goop in a tube" does indeed make your gun "temperature sensitive" or the "dieseling" still stays the same or gets worse you'll be doing a proper disassembly internal stripping and re-lubing. The only thing I found that makes for a long term consistent shot cycle was installing a snug fitting spring guide along with proper lubing.

Still, if dieseling is your ONLY issue perhaps it's better to simply stop with the "excessive lube" and let the stuff "burn off" if the dieseling is only a bit of smoke from the muzzle after the shot. If the dieseling is an actual "detonation" evident by a crack when shot I PERSONALLY believe that a disassembly, stripping of the excess lube, then relubing sparingly with "springer appropriate lube".

One drop of oil was excessive?  I had already known that my nitro piston airguns get quite hot, like the compression fire starters.  That is why I tried the high temp silicone oil.  I had no idea that they get hotter than 500 degrees.

As for the dieseling, it made progressive smaller detonations for 4 shots.

I appreciate everyones recommendations and info.  Since nitro pistons don't need grease, I decided against getting the grease in a tube.  I noted the "springer appropriate lube" so what is the consensus for a nitro piston lube?

[nced]

Thanks James.  I will order some.

Clicked the link about the crossbow.  That thing looks tedious and clumsy.

It might be good to read this thread............
https://www.gatewaytoairguns.org/GTA/index.php?topic=191953.0

My experience with "goop on the spring" to kill twang and vibrations was less than satisfactory because the stuff I used (heavy tar shown in my posted pics) was initially good for killing "Beeman R9 twang" however the "fix" was temporary at best. The downside was that the "goop" made my guns' velocity dependent on the atmospheric temperature so accuracy was also affected. I don't know anything about the "tune in a tube" stuff so perhaps your mileage may vary. Still, if the "goop in a tube" does indeed make your gun "temperature sensitive" or the "dieseling" still stays the same or gets worse you'll be doing a proper disassembly internal stripping and re-lubing. The only thing I found that makes for a long term consistent shot cycle was installing a snug fitting spring guide along with proper lubing.

Still, if dieseling is your ONLY issue perhaps it's better to simply stop with the "excessive lube" and let the stuff "burn off" if the dieseling is only a bit of smoke from the muzzle after the shot. If the dieseling is an actual "detonation" evident by a crack when shot I PERSONALLY believe that a disassembly, stripping of the excess lube, then relubing sparingly with "springer appropriate lube".

One drop of oil was excessive?  I had already known that my nitro piston airguns get quite hot, like the compression fire starters.  That is why I tried the high temp silicone oil.  I had no idea that they get hotter than 500 degrees.

As for the dieseling, it made progressive smaller detonations for 4 shots.

I appreciate everyones recommendations and info.  Since nitro pistons don't need grease, I decided against getting the grease in a tube.  I noted the "springer appropriate lube" so what is the consensus for a nitro piston lube?

Heat around the transfer port of piston guns is hot enough to do this, especially with excess petroleum based diesel prone lube..........

LOL, piston seal face erosion at the transfer port is ONE of the reasons I've been using home turned oring sealed piston caps made from 6061 T8 aluminum for my personal springers (no seal face erosion with metal).........


Here is an example of the very first oring sealed piston cap I made decades ago after about 1000 shots compared to a new "old HW design piston seal". I was using molly paste as a lube at that time and the aluminum piston cap face shows some "burned molly paste residue" that migrated into the compression area even though the paste was sparingly used and not applied to the piston seal face.........
 

[Mitch]

WOW, you guys are really into this sport. 

[Michael M.]

Bought a screw type clamp because my squeeze type couldn't do the job.  Applied a tiny amount of automotive moly grease on the edge of the piston and the metal part it is attached to.  Took me a while to figure out how to get the trigger mech back on though.  A little dental floss did the trick.  Now it doesn't squeak and shoots a lot smoother.