Lubricant: mineral oil: detonation: PCP compression temp

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Gabpan

Gabpan

Member
Mar 29, 2020
123
1
MI, United States
The standard lubrication for PCP is silicone oil. This is seemingly for many reasons including longevity of the internal components such as o rings in addition to preventing detonation by using non combustible oil.

I have been using mineral oil in break barrels and powder burners with no issues. I like the stuff and would like to use it in my Benjamin maximus (which is working out very well thanks for the suggestions on what to buy). 

Using mineral oil I am not worried about the rings. My concern is combustion. I have not found any real data on the web to make an educated judgement. The flash point for mineral oil is readily available. What I can not find is the temperature generated by the rifle when the compressed gas is released. 

So on a side note my maximus has been working out great however I noticed the bolt requires a considerable of force to cock. Specifically the pulling back is a hard pull. Am I correct in assuming that this is normal for PCP air rifles in this price range? It requires much more Force than a powder burner bolt action. I assume this is because I'm fighting the pressure of the tank when I'm cocking it. 
 
When gas goes from high pressure to low pressure, such as in firing a PCP, it gets colder. Thats how refrigeration systems work. 

Springers work the opposite, they compress air on firing, going from low pressure to high, and that creates heat and lots of it and will detonate. 

Now when filling a PCP, you can get some warmth on the tube. 

Silicone does absolutely nothing for lubrication of metal parts. It's a great rubber lubricant, and that's all. Don't use it on metal. It's fine for lubing orings in a PCP. 

That said, I've just used regular grease or motor oil in mine for a long time. Not telling you too, it's just what I use because I always have it handy. 

When cocking your gun, you are compressing a heavy spring along with the hammer. That's the resistance you feel. It's normal. But if it's gritty feeling, a light oil may help there. 
 
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There is a general misconception about the use of silicone in PCP rifles. Not only is it a poor metal lube, when subjected to high heat/pressure it can cause seizing of metal-on-metal parts. I'm sure there are many good lubes. On the advice of a respected rifle builder, I've been using mostly Mobil 1 synthetic motor oil for metal lube. If I think an O ring needs lube, I use Dow O ring lube, just enough that I can barely feel it on my fingers. For O rings in static use, I usually don't lube. There is endless discussion on this, and I'm sure there are many satisfactory answers, but this seems to work well for me.
 
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dont know about mineral oil, its a good laxative i heard .. a quick google of mineral oil flash point temp should answer your question ...silicone oil is great for orings AND corrosion prevention aroumd them, maybe not perfect but better than nothing .. as far as lube on metal parts a polish and treatment with something that contains moly is the best solution .. gooping up a guns action with messy gobs of oil and grease is amateur ..
 
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FP10 and the old Beeman MP5 oil(now marketed by Air Venturi @ Pyramid) is the only external lubes to a PCP I use. Internal moving parts such as mag indexing levers, the portion of the pellet probe not exposed in the mag well to tip, get moly paste, hammer springs, hammers, hammer spring guides all get a light dust of moly powder(some guns, not all), and nickel anti seize on all fasteners or some threaded parts. For stocks aof all kinds, a light spray of silicone oil for the shine and protection. Simple.

I think some of these home brew concoctions are what gets us in trouble not immediately, but later on in failed o rings, leaks, seized up parts, stained wood stocks. I say leave the automobile lubes for what they were intended for, cars and trucks, and stick with what’s been used and made for Airguns. I’ve heard of suggestions like dipping o rings in tranny fluid to get them to expand and seal better. Just swap out for a thicker CS o ring! 

Its the low flash point rating that will make certain lubes dangerous in Airgun use. The higher the flash point, the safer it is. Check the MSDS on a type of lube before using it.
 
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Moly paste will thicken and gum up over time, and cause parts that move to not move anymore. Be careful where you put it. Great stuff in the right places though. 

Concerning flash point, tell me again which part of a PCP gets hot? 

Just an FYI: the flash point for FP10 oil is LOWER than the flash point for Mobil 1 5W30 engine oil by 54 degrees..... Obviously this means the "airgun oil" will combust at a lower temp than the "automotive oil". 


 
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Moly paste will thicken and gum up over time, and cause parts that move to not move anymore. Be careful where you put it. Great stuff in the right places though. 

Concerning flash point, tell me again which part of a PCP gets hot?
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I think most lubricant makers use high pressure and high heat as generally comparable issues in developing their products. In PCP rifles, any metal-to-metal connections that are subject to the operating pressure of the rifle are locations that should receive such specialized lubes. These would also be areas to avoid with silicone. I'm not a metallurgist, but that's my understanding. 
 
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What happens in chamber? Its in atmospheric pressure and hammer hits in valve - > pressure coming from container start to equalise with chamber pressure untill force in chamber is high enough to overcome friction - > higher friction projectile you have in chamber equals higher pressure you need in chamber - > more likely you get detonation. Really hard to achieve in low friction low pressure pellet platforms but have happend many times in bigbores. There is even one well reputated airgun world record holder and builder who managed to get detonation with 357cal airgun while firelapping barrel with wheeler barrel lapping paste. Also one thing ppl dont seem to realise is that fast moving air has its own high friction happening also.

There is no reason or place to use anything that can light up in pcp....
 
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What happens in chamber? Its in atmospheric pressure and hammer hits in valve - > pressure coming from container start to equalise with chamber pressure untill force in chamber is high enough to overcome friction - > higher friction projectile you have in chamber equals higher pressure you need in chamber - > more likely you get detonation. Really hard to achieve in low friction low pressure pellet platforms but have happend many times in bigbores. There is even one well reputated airgun world record holder and builder who managed to get detonation with 357cal airgun while firelapping barrel with wheeler barrel lapping paste. Also one thing ppl dont seem to realise is that fast moving air has its own high friction happening also.

There is no reason or place to use anything that can light up in pcp....
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ONE TIME, many times, do you have a link? was there any damage or just a bang with no damage or injury? let us be real, I do not live in fear of what if, details are king, what pressures behind the valve, what lubes were used, many questions
 
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So from what I gather I had the thinking wrong on this one lol. I get it springers compress whereas PCP releases air in simple terms.

I use mineral oil in the break barrels never had a seal problem. It was actually suggested in an email I sent Hatsan regarding lubrication for the Hatsan edge break barrel. For powder burners I will mix the mineral oil with molybdenum grease and apply to parts that slide. I apply heavy but on my pb's I clean after each use.

I could go the mainstream and use balistal or something like it but it's one more thing to buy that takes up space.

Thanks everyone for the enlightenment.






 
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Moly paste will thicken and gum up over time, and cause parts that move to not move anymore. Be careful where you put it. Great stuff in the right places though. 

Concerning flash point, tell me again which part of a PCP gets hot? 

Just an FYI: the flash point for FP10 oil is LOWER than the flash point for Mobil 1 5W30 engine oil by 54 degrees..... Obviously this means the "airgun oil" will combust at a lower temp than the "automotive oil". 

Click to expand...

Re read my post- for external areas I use FP10. Inside the HPA area like air tube and pre valve, silicone grease or oil only.
 
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