oiling compression chamber


January 3, 2014, 07:45 PM
I have a Crosman TR77 NPS. The owners manual says to oil the compression chamber occasionally. I put one drop of oil in the chamber last night. This morning before I went to work I figured I'd shoot the gun. The first pellet I shot made a sound like a .22 LR. KaPOW! and a bit of smoke came out of the gun. The next shot was right back to normal. Is this normal?

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January 4, 2014, 12:36 AM
Perfectly normal. It's the oil burning. New guns are usually much worse. I usually use a drop or two of thin motor oil, preferably synthetic like Royal Purple, or Lucas gun oil. Then 1-2 shots are loud, then some smoke for maybe 10 shots and you're good to go. Many insist on silicone, but that's not a good lube, syn motor oil is the best imo.
I'd also add a drop or two of thicker motor oil to lube the piston skirt where it scrapes under the scope rail. Let some oil soak into the cocking linkage pivot points, and some, or grease on the cocking shoe. Oil or grease the barrel pivot point and detent plunger, and grease the detent face. All maybe every 1000 shots? I can go into more detail and what lube is better where if needed...

January 4, 2014, 12:42 AM
I'll take whatever knowledge you want to pass. This is my first pellet gun and to be honest I almost couldn't find the compression chamber. :uhoh:

January 4, 2014, 02:30 AM
Here's a good run down on this


January 4, 2014, 10:32 AM
Be REAL careful what kind of oil you put into the chamber of an air gun. The loud sound you heard is likely combustion in the chamber - something you DO NOT EVER want. Combustion can ruin piston seals quickly.

Oiling of a chamber should be very rare, and only a synthetic oil designed specifically for air guns should be used. Do NOT use normal oil. Synthetic oil is designed to not combust (detonate or diesel) at the high chamber temperatures of a spring piston air gun.


January 4, 2014, 10:52 AM
I used Crosman synthetic oil that I found at the store…it was the only one they had but I believe it was also the one recommended in the manual. It's a red fluid.

January 4, 2014, 12:06 PM
Many expert air gun tuners state that the only seal that should be oiled is a leather seal. Leather seals are pretty much no longer used in modern guns, synthetic is in.

The noise you heard is called dieseling. Many people are not aware that for an instant, temperatures in the air port of rise to over 1000 degrees and will ignite mineral based oils.

The problem is that when the oil ignites it puts undo stress on all the internal components and it could easily mess them up.

I know the manual says to oil the chamber on occasion and most would suggest following the manual. I am not saying not to do that, just be very cautious not to overdo.

January 4, 2014, 11:23 PM
Gspn, looks like you got what was supposed to be the right oil. I did not know synthetic oil could detonate, so I am a bit confused as to why it happened.

Unless you shoot A LOT, you should almost never ever need to oil the chamber. I recently had a match spring gun tuned up and I asked the 'smith how often I should lubricate the chamber and his reply was basically, "Don't bother." Here is what he said:

"I would not lubricate the internals, the lubricants [that I used] bond to the surfaces and do not need anything else, you just need to clean the bore with a pull through and without any bore solvents at all"

January 5, 2014, 02:08 AM
Virtually all lubes will diesel in there. There is only one oil type lube I'm aware of that won't ignite in there, so I'm told, and it's both hard to get and very expensive. I believe they say to use the special chamber lube for two reasons; one is to keep people from using really nasty ones like WD-40 which really light up, and two because nobody will pay $5 for 1/2oz of motor oil.

Sure dieseling isn't good for it, but is it really that bad? I've never seen any reason to believe a drop of motor oil will hurt the gun. I've heard people insist it will, but there's lots of mystery shrouding the springer airgun and 99% of people are just repeating what they heard and a lot of that came from someone who didn't have a clue. Then there's all the outdated info that people accept as fact and even the mfg's perpetuate to boost sales. A lot of wives tales and exaggerations imo... Maybe some people are unable to differentiate between a drop of oil and a blast of WD-40?
If it was so bad then why does the factory put all that nasty grease in there that diesels? At least syn motor oil is top notch stuff to use.
I don't use the special silicone oil because it's nasty and it's not lube. I use motor oil for three reasons, one is it's outstanding, two it prevents rust in the chamber, port, and barrel. Three it helps power the same way castor oil helps a 2-stroke dirt bike, if you understand that.
Silicone chamber lube usually reduces power, and you do not want that crap getting further back on the piston skirt and such where it actually needs lube so what's the point? So people can use silicone because they've been told to by someone who sells it, it doesn't affect me. I will continue to use motor oil and never have any problems.

January 9, 2014, 12:48 PM
Dieseling is considered an issue in South Africa for air rifles. I can't find the link I had for it but the way the doctor was talking about the issue. Dieseling somehow made the air rifle a great deal more powerful. I wouldn't think that per se since the charge of ail wouldn't be that great but they are stating a twenty to thirty percent increase in velocity which again I don't really see at that big a deal because of the twist rate of the barrels being set for certain velocity ranges anyways (resulting in inaccurate shooting).

I thought about designing a gun completely around the concept of dieseling and PCP air guns just for grins and giggles (and to use the idea in a fictional book if it looked possible and useful) but from every angle I approach it it just doesn't look like the gun would last that long because of the seals.

January 9, 2014, 03:14 PM
MagnumDweeb: It's true dieseling makes more power, how much depends on the type and quantity of oil, and the gun in question. Some people do make them diesel hard to get the most velocity for entertainment, but it's really pointless for anything but entertainment. They'll spray a small squirt of WD in the port and BAM! Power is way up. I've done it using WD-40, but only with a useless gun that was otherwise headed for the trash. I also know about using oils in other guns because that cannot be avoided, but those oils don't explode like WD. If you do it then I'd use regular motor oil first, maybe 3-4 drops and see how much power and for how many shots it lasts. If that's not enough power them try WD-40. I suppose stuff like alcohol or even gasoline would really bump power, but I've never been brave enough to try it for fear of injury to the gun or myself in one shot. Yes dieseling is harder on the seals due to the extra heat and pressure, but normal dieseling with normal lube for maintenance doesn't seem to be an issue. I've heard it's also hard on the spring by sending a shock wave thru it from the extremely fast change of direction, but the gun I used was fine, and so was those of other people I know who tried it. It may be harder on the scope too but I'm not sure so it's up to you to use a scope. The rifling isn't an issue, but the velocity is all over the place because you can't make the mix the same for every shot. The muzzle blast will be much greater and many pellets will go super sonic, so between those things your accuracy is probably gone.
Not sure what you meant about pcp guns, but I don't see how you can get them to diesel. It's the heat that ignites the oil, and a pcp makes a cold blast of air, not a hot one like a springer.
So for fun I'd only use a disposable springer. The seal life would depend on the material of the seal and how violent the explosion. The spring life I can't say, but a nitro spring shouldn't have any problem with it. Maybe experiment, try a generic springer and inspect the seal, preferably use a new seal, then shoot maybe 20 shots with WD-40 and take it apart and look at the seal. I'd also test velocity before and after to see if the spring has weakened.
For your book I can't say since I don't know the story, but I can give my best guess if you tell me.

January 18, 2014, 08:28 PM
Y'all need to visit the Gateway to Airguns forum.
You'll find all the airgun info you need.

Yes, a drop of oil every now and then will destroy your seal.
One drop of oil has a lot of power when it's vaporized, compressed, and ignited.
I've seen some very nice springer piston seals ruined very quickly by dieseling.
I've seen them recock on their own, from dieseling.
It tears the hell out of the seals.
Don't do it, unless you don't mind breaking springs and destroying seals.

I personally destroyed a seal on a nice springer from dieseling.
It was an expensive lesson. It was fun until I had to replace the seal.

I've also packed black powder into the skirt and even crushed match heads into the skirts of pellets. Sounded like a .22 going off. Penetration was pretty phenomenal.
I did that with a powerful Chinese springer. One I didn't care about.

I don't recommend it.

There was a springer once, that was intended to be dieseled.
IIRC, you used ether as the fuel.
Can't remember specifics.

January 19, 2014, 04:11 PM
As you can see, there are a bunch of different opinions as to whether or not to oil the chamber.

One post gives specific examples of how it destroyed his seals another considers it to be a "wives tale".

When seals were made of leather, oiling was important to keep it flexible. Why would dieseling not hurt a leather seal but kill a synthetic seal??? Well, a synthetic seal is a lot harder than a moist leather seal and it does not have the flex that a leather seal does.

A gun with a leather seal works best with a perfectly smooth chamber and that is part of the "tuning" process while a synthetic seal does better in a chamber that is very lightly cross hatched honed with a surface coat of molly lube on it. The cross hatches hold the molly like the piston in a car holds oil for lubrication.

One thing that is important to do is run many patches through the barrel of a brand new gun. Many manufactures will oil the barrel to prevent rust while stored and waiting purchase. My friend brought me over a new gun once and jumped right into putting a pellet in it and letting it fly. The report was easily as much as a high velocity 22 or more. The smoke was spectacular and his face was that of horror. All I could say was I told you so.

That one shot may have done it because the gun had no accuracy at all but I am comparing it to my guns and that is not fair.

January 19, 2014, 05:00 PM
Mouse: The loud dieseling was from the grease in the chamber and is normal for a new gun, it had nothing to do with anything in the barrel.
If his gun is inaccurate then it's simply an inaccurate gun as many are. Most of these guns are made in places other than Germany, US, or UK, and all those guns are a gamble. You can try playing with it, like crowning the barrel, or cutting 1/4-1/2" off the barrel and crowning. If all fails buy a new barrel which I have done many times.
I oil my chambers more often than normal and my seals are in exceptionally good condition which is why I don't believe it hurts them. Btw, all the guns I've seen came with mirror finished bores, but I usually sand them which holds lube as you said and seems to make more power which I assume is thru less friction. An engine bore is sanded for a different reason, but both have advantages.
I don't recommend moly paste, but that's a whole new can of worms to open.

January 20, 2014, 07:00 PM
You are correct, the dieseling in my friend's rifle came from the oil in the chamber, not the barrel. I was thinking of something else when I wrote that.

Honing a chamber does keep lubrication ( 65% or more Molly as per many respected tuners) in place in that it has small nooks to hide in as the seal slides by and provides just the proper amount of lube to make the process smooth. In a car cylinder, it also holds oil and breaks the glaze to seat the rings.

I suspect that over oiling is more detrimental to super magnum air rifles because they are somewhat stressed to begin with.

There is quite a difference between dieseling and detonation as explained here but oil in the chamber can lead to both. The question is how much oil does it take?


January 20, 2014, 11:00 PM
I just don't like the moly paste they sell for airguns is all. I use tungsten disulfide and a thin non-sticky grease which makes for a better lube and more power. I don't know how much chamber oil would be considered minimum, but I personally don't have a problem with oiling what most would consider too much. Not that I put too much in at a time which would be a waste, I just oil more often to be sure it's oiled well and so I don't have to worry about rust.

January 29, 2014, 12:52 PM
I use the Crossman air gun oil.

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