why is oil in a barrel dangerous?

**vaughan** · 30-09-2008, 22:14

please can somebody explain this one to me? I have read it has to do with pressure build up but how does this cause a problem?

confused0083

**Corné** · 01-10-2008, 07:48

Oil forms a barrier between two moving parts as to reduce friction and thus wear and tear. The bullet and barrel are made to specific tolerances and needs to fit/touch one another. If you add oil it will be between the barrel and the bullet. The bullet is already at a tight fit and the oil will decrease the barrel diameter by the thickness of the oil in the barrel. The bullet thus has to squeeze through a 'smaller' barrel and thus the pressure increase tremendously due to the higher resistance that the bullet encounter. Oil reduced friction by forming a barrier that is not easy to compress. The properties of oil is such that it does not compress where water can be compressed. Look at hydraulic lifting equipment. You use in effect oil to do the job. The reason being that oil will not compress and can resist pressure. In a pressure situation the weakest link will give in and it ain't going to be the bullet nor the oil....it will be the barrel. The barrel can either bulge or rapture. I would reckon that in the same way the deeper a bullet is seated, the pressure escalates exponentially, the same will apply to oil in a barrel.

**vaughan** · 01-10-2008, 08:48

I see, was not thinking that the oil actually leaves a thin layer in barrel and wont give way! thanks

**Count Bla** · 01-10-2008, 12:43

Corne, I tend to disagree with you somewhat. Please note that this logic makes sense (to me) w.r.t. hand guns, but rifles might be a different animal due to much higher pressures, depending on caliber.

I agree that too much oil MIGHT cause a SLIGHT pressure rise, I don't think its a very dangerous situation.

Let me explain why I think so (and I might be wrong). You mentioned in your post that water is compressable. This is not entirely true. The majority of physics calculations will accept the density of water as 1 for all pressures and the compressability of water is seen as negligible. The same is true for oil. However, you can shoot your Glock under water (as long as the barrel is completely filled with water) without failure. Haven't tried it myself, but know some people who has.

The viscosity of oil, however is somewhat higher than that of water at room temperature. However, under pressure (such as when a bullet is fired through an oiled barrel) the oil will heat up instantaneously and change viscosity to pretty much that of water (gun oil is not that viscous to start with anyway). I think excess oil will most probably just be pushed out in front of the bullet, allowing only what fits between bullet and barrel.

I agree that excessive oil might cause a better "seal" between bullet and barrel, but it should still be OK as long as the ammo does not exceed maximum pressure levels.

As far as oil is concerned in hydraulic equipment, it has a lot to do with the heat absorption/transfer rate of oil as well as the viscosity factor which makes sealing of cylinders/valves easier. The corrosion protection is also a factor. Water will just leak due to low viscosity and probably start boiling off under high pressure. Those in the hydraulic equipment industry will be able to give more technical info.

Feel free to disagree since this is only my train of thought and not based on any actual or factual data. Only experience that I have is that I oil the barrels of guns that I don't shoot regularly quite heavily and usually thats cleared up with the first shot on the range. No problems yet.

**Corné** · 01-10-2008, 13:21

Count Bla,

Ok my reference to water in hydraulic equipment - I am just ignoring the corrosion issue as I did not see it relevant (maybe incorrect). It was more of 'besides the corrosion issue'. Can't argue to much with your post either.

I also have not shot my Glock under water but it would be interesting to see what would happen if you shoot it submerged in oil?

I just know from way back that I have alway's been told not to shoot with oil in the barrel.

**Count Bla** · 01-10-2008, 13:39

We also learned from our dad that you oil a hunting barrel for storing, but dry it prior to use. I believe accuracy has more to do with it than fear of blowing the barrel.

I did a google search on the topic and found nothing related to danger, but rather to the collection of dust and the effect excessive oil has on accuracy. Thus, I came to the conclusion that if you oil your barrel with a rod & oily cloth, you can't really over oil it to the extent that it becomes dangerous.

As to shooting a Glock submerged in oil...lets use your Glock for that one. ;D

**Armed Preacher** · 01-10-2008, 17:35

When a bullet is forcing its way down the barrel and it finds any obstruction (water, oil, dust, potato etc) to its motion there are 1 of 3 things that will occur (there may be many more to the scientists out there).
Either the obstruction is instantly accelerated the moment the bullet touches it, (or in the case of a full obstruction, the moment the pressure behind the obstruction but ahead of the bullet, overcomes the obstructive force and moves the obstruction before the bullet touches it) or the bullet must come to an immediate standstill when it touches any obstruction OR the bullet must be able to squeeze past the obstruction.
Clearly option 1 & 2 are not viable so option 3 is the only one left.
For the bullet to squeeze past the obstruction, it stands to reason that the obstruction must have some other space to move into. If the space available for the obstruction to move into has less volume than the obstruction itself and the bullet cannot shrink instantly, then what we have is a blockage. There is so much pressure behind the bullet that there is no way in heaven or hell (sorry, must try and get some theology in here somehow :)) that the bullet can stop, it has no option but to force its way past this obstruction and the only way to do this is if the barrel expands at that point. This barrel expansion may be in the form of 'plastic' or 'elastic' deformation, elastic meaning stretch and come back to original size ::), plastic meaning either stretch and stay stretched or stretch and shrink, but still remains larger than original size confused0068.
The bottom line is that oil in your barrel could lead to permanent expansion (damage) to your gun so why take a chance, clean out all oil before you take a shot unless of course you have a spare barrel lying around as a replacement :police:

**Mike** · 06-10-2008, 11:49

This is more so for long guns than handguns. As the bullet moves forward (very very quickly) it pushes the oil ahead of it causing a "wave" of oil at the contact point between the bullet and the barrel. About halfway down the amount of oil collected causes the wave to slow down causing the bullet to "overrun" it in a process well described in the above postings. This causes the bullet to slow just a tad in the barrel causing more pressure to build than is normal. This is why an oily barrel will give you more felt recoil. Enough oil and you've just screwed the barrel

**Johann the Horrible** · 02-11-2008, 22:35

Amen! to the above posts. A little oil you can maybe get away with but sooner rather than lather your barrel will resemble a pregnant earthworm. (Bubble in the middle) After that stage you will see a lot of surprised looking buck as they disappear over the horizon. Guys with bulged barrels soon forget how venison tastes.