Lube Purging, What Is It?

Lube Purging, which of the following 2 explanations correctly defines it?

Possible explanation #1) - I thought lube purging occurred after several shots were fired, coating the bore with BP fouling that is heavily saturated with bullet lube (softened or liquid). When a subsequent shot is fired, all the soft lube saturated carbon fouling is pushed out of the bore by the bullet acting like squeegee cleaning water off a glass window. The column of muck being pushed forward by the bullet is blamed for causing that shot to be less accurate than the previous shots as it impacts away from the tight group that had been forming prior.


Possible explanation #2) - As the bullets lube groove(s) exit the bore the high centrifugal force generated by the rifling spinning the bullet at high RPM causes the lube in the groove to be flung out of the groove, purging the groove of lube and creates a lube star on the muzzle.
An accuracy robbing problem occurs if the groove is only partially purged creating a rotationally unbalanced bullet which impacts the target off the point of aim out of the group.

If the question is resolved, I'll have this to blame for all of my 'flyers'.

A good lube formula will leave the barrel in the same condition after each shot. In the Lube Quest thread, Eutectic coined the term CORE condition (Consistency Of Residuals Encountered)
.
When certain lube ingredients are used in a lube formula in too high of a percentage, these are typically, ingredients that provide too much "slick" to the formula. There is a microscopic buildup, shot to shot, of that "slick" ingredient. After enough of that ingrediant builds up, it is purged by the next boolit.
.
Anecdote:
I came up with a improved version of Speed Green, using a Amsoil product instead of Bullplate. The Amsoil product is a PAO based lube, whereas Bullplate is likely not. PAO has a high "slick" factor to it, which I didn't know about at the time. I loaded some revolver ammo with it, and I experienced a flyer every 3rd or fourth shot. After the Lube Gurus explained this to me, I lowered the percentage of Amsoil product in my formula, and the flyers ceased to occur...proving my problem was lube purge flyers.

Quote:

---

Originally Posted by greenjoytj

Lube Purging, which of the following 2 explanations correctly defines it?

Possible explanation #1) - I thought lube purging occurred after several shots were fired, coating the bore with BP fouling that is heavily saturated with bullet lube (softened or liquid). When a subsequent shot is fired, all the soft lube saturated carbon fouling is pushed out of the bore by the bullet acting like squeegee cleaning water off a glass window. The column of muck being pushed forward by the bullet is blamed for causing that shot to be less accurate than the previous shots as it impacts away from the tight group that had been forming prior.


Possible explanation #2) - As the bullets lube groove(s) exit the bore the high centrifugal force generated by the rifling spinning the bullet at high RPM causes the lube in the groove to be flung out of the groove, purging the groove of lube and creates a lube star on the muzzle.
An accuracy robbing problem occurs if the groove is only partially purged creating a rotationally unbalanced bullet which impacts the target off the point of aim out of the group.

---

#2 definitely occurs. Observe the lube on the face of the Oehler Skyscreens. The start screen was 15' from the muzzle. This was at high rpm during HV test of 6.5 bullets in a 6.5 Swede rifle.

Attachment 312333

I was chatting with a guy one time about lube purging. His take on the subject was that it occurred more in the summer than the winter while shooting the same lube, bullet, rifle... So his solution was for summer/warmer conditions was to lube less of the lube grooves on the rifle bullets. This was for smokeless 30 cal milsurps if that makes any difference.