If you clean the bore and it is not totally dry before firing (just a bit of an oilfilm left) you see higher impacts on the target and also a bit to the right (1 - 4 inches high at 100 yards).
a. Bullet lubrication gives less pressure, less velocity at the muzzle?
b. Pressure the same, less bullet resistance and a higher muzzle velocity?
c. Oilfilm is an extra resistance, pressure rises and more velocity?
d. Oil in the chamber enhances the higher impact, why?
I know how to clean and dry the bore and chamber, that's no problem.
I'm very interested in your technical comments on this phenomenon, thanks.
Nice day,
Jan.

Easy,

Oil in bore will aid velocity....

since you have a right hand twist in your rifle, the first shot will be to the right, and high due to faster velocity...

Slower velocity, it should be down and to the left...

The reaction to an oily bore seems to change from rifle to rifle. I believe I often see more of a reaction in a thinner barrel.

I don't know what the exact reason is, but I once saw a test in a German hunting magazine trying to establish the effect of an oily bore on the first shot. Their conclusion was that an oily chamber had the most effect on POI. I don't know the exact reasons for this, but one might speculate it had something to do with the oil preventing the case from gripping the walls of the chamber. I know a fired case comes out of an oily chamber feeling oily.

Apart from factors of external ballistics such as muzzle velocity and ballistic coefficient, POI is to a large degree dependent on barrel vibration when the bullet leaves the barrel. Barrel vibration will be determined by any number of factors. I am not convinced you can draw conclusions from observed POI to assumed muzzle velocity. If you really want to verify if an oily barrel has an effect on muzzle velocity, you'll have to chronograph with and without oil.

- mike

IMHO---oil in the bore actually INCREASES pressure and therefore velocity.
A bullet under high velocity and pressure trying to push fluid away ((I feel) makes more pressure.

I was tought that when cleaning a rifle the last thing you do is run an oily patch through the bore then one clean patch. The idea is that the bore will not be dripping oil but just a trace of oil is there to lubricate the first shot. After that the gun powder will lubricate the next shot due to the graphite in the powder. Although the bullet impact is slightly different it isn't by much. Pressure has never been an issue for me.

I know the effects described above, too.
However: Even with a perfectly degreased bore (using carb cleaner or isopropylic alcohol) the first shot out of the cold bore is still at 2 o'clock. When I don't shoot foulers on the range, I hold under and left 1 to 2".

quote:

I was tought that when cleaning a rifle the last thing you do is run an oily patch through the bore then one clean patch.

Before firing a gun,I run a tight fitting dry patch through the bore to remove as much oil as possible.Oil in the bore increases pressure as kraky has posted.

I should think it would burn into a nice layer of carbon for you to clean.

Thank you, folks, so far.
Yes, I do know you should always fire a dry bore (except for a specific break-in procedure), but that's not the issue here.
I wondered why all the impacts rise and go to the right. Yes, to the right could be due to the r-h twist. But, higher velocity does not always mean you get a higher POI, due to the Optimal Barrel Time and harmonics. But what is even more interesting to me: why does an oily chamber enhance this POI so much, even with a dry bore?

Seafire could be right, anyway, but again: why do all impacts rise, pertaining to the OBT?
MHO: thank you. I think we're talking about the same investigator, Norbert Klups from Germany. He issued a handbook on ballistics in which he describes the same shift of POI with an oily bore and even more with an oily chamber. Even with a totally dry bore, he said, but with an oilfilm in the chamber you will see a significant higher POI. He had no explanation.
Kraky: I think you're right, we're on the same page, I guess.
Buckshot: I think the friction of the bullet is so tite that it will leave no oil at all after firing. The bore will be dry behind the bullet. No extra carbon (IMO).
Thank you again,
Jan.

Jan, you are right, it could well have been Norbert Klups who wrote the article I referred to. It is a couple of years back, so I can't remember the details. But the thing about the oily chamber stuck in my mind. In any event, it was an interesting experiment - even without a final explanation of the effects observed.
- mike

quote:

Oil in bore will aid velocity....

While that may be true you run the risk of damaging the bore.

Oil like any fluid cannot be compressed and could be forced into the pores of the bore enlarging them enough to cause pitting.

I strongly urge everyone to run a tight dry patch through before firing.

Oil should only be used to protect the bore while in storage, not for any lubricating purposes.

shooter's choice and your ok when shooting.bore is slick even when dry patching.oil only to store then clean her out with sc,then dry patch.This process will put the first round in for score.so.remember sc then dry patch before shooting a group.