gun oil causing chamber pressure

[Koda]

You will note that the shooter up-ended the bores and let them drain before shooting. Excessive fluids or grease in the bore can form an obstruction, just as any solid can.

I was actually amazed they didnt let the bore drain longer than they did. Left me wondering how motor oil could be pushed down the bore safely by the bullet.

 

[Jay Walk]

Is that why .22 match ammo is sometimes all lubed Up?
For a better seal?

 

[gmerkt]

I was actually amazed they didnt let the bore drain longer than they did. Left me wondering how motor oil could be pushed down the bore safely by the bullet.

I don't know and don't want to find out; caution is advised. I shudder when I think of what we used to do as teenagers - and young 20's. I seem to recall hearing the phrase, "just shoot it out." These days, I won't even leave the thin coating for storage in place, I patch the chamber (for reasons stated previously in the thread) and the bore before shooting.

Yes, the guy in the video didn't let it drain all that long. Here's the deal. When you leave a heavy coating in like that, when the bullet is fired, all the oil is pushed ahead of the bullet. If the aggregation is large enough, it might create it's own form of obstruction. Said another way, enough will be scraped along and come together as a lot. Maybe the dynamics of it lessen the possibility, rather than having the bullet encounter a sudden, static obstruction. I'm not sure, but as I saw, it's for someone else to work on, not me.

 

[DLS]

A little historical info. One of the contributing factors in the early Springfield 1903 receiver failures was found to be either oil on the cases or bullet lube that had melted and run down onto the cases. This was at the National matches and very very well investigated and documented in Julian Hatcher's notebook (he did the investigation for the military.

Hatcher himself recinded these conclusions some years later.

What was later found to be the over pressure culprit was galvanic welding of the bullet case to the cartridge neck due to a new alloy used to jacket the bullets.

Intact bullets were found downrange with entire case necks welded to the bullet base. In effect, the projectile diameter was the bullet diameter PLUS the added thickness of the case neck.

This raised pressures to insane levels.

The new alloy was a abandoned for use as a bullet jacket material.

Oily cases have little to no impact on chamber pressures. Brass flows at 12 - 15,000 psi so the idea that the case has influence on bolt face pressures is not true.

Several early machie guns designers exterminated with oiled cartridges to ensure ease of extraction but that was abandoned due to the mess that was made trying to use oily cartridges in the feild, not because it caused any issues during the firing of the gun.