Known Loads too hot now..why

[Pdvdh]

The dynamic viscosity of water versus oil at ambient temperatures, not internal engine temperatures, is about a factor of five difference. This is why it will provide more bolt thrust than an oiled chamber. If you take Varmint Als calculations and guesstimate where bolt thrust would be with water you easily get into the areas where he says it is not possible to go. You then do not need to be over pressure to get heavy bolt lift.

What's the relationship between dynamic viscosity and friction reduction between a brass cartridge and a steel chamber? I know there is a relationship between dynamic viscosity and friction for purposes of fluid flow in pipes and open channel fluid flow. Didn't know any relationship existed between dynamic viscosity and friction coefficient modification between two pieces of steel or a piece of cartridge brass and steel.

I would expect the very best friction reduction lubricant to be the same lubricant that best reduces friction between a fired cartridge case and a full length resizing die (brass and steel - just like in the rifle chamber). Have you ever tried lubing fired cases with water prior to resizing? Did it reduce friction better than Imperial Sizing Die Wax.

I expect there are some lube oils that will yield a lower friction coefficient than water. The lube that provides the greatest reduction in friction is the one that will result in the greatest bolt thrust.

 

[Pdvdh]

No I only shot the SAUM. It is what I'm trying to focus on now. It is just R-P brass.

Yes it shot poorly, but it is a new gun to me, so it might have been user error.

Did you get to shoot at 1000yds? Where do you shoot? Just off the highway?

I don't know if I'll be wetting my cartridges any time soon. I think I've learned my lesson...

Too windy down on the Kenai to shoot at 1000yds today. I've got a power line and natural gas line easement where I set up. But with the frost still in the ground and spring break-up, it's also too muddy to drive in there right now. I walked it today and it a no-go for vehicle travel for the time being.

Reason I asked about shooting good versus shooting poor is the case pressures are likely the same - wet cartridges or dry cartridges. But if the bolt thrust force is greater with the wet cartridges compared to the dry, then I suppose that could alter group size and point of impact too. Good reason not to hunt in the rain. I've become more of a fair weather hunter as I get older. Now I've got an excuse!

Anyhow, glad your reloads are back where you expected them to be - pressure signs wise. One less mystery to be concerned about.

 

[bigngreen]

Right on man. It seems that an answer has been rendered.

 

[Pdvdh]

I just came across this on Nosler's web site:

"When cleaning the rifle between firings, make sure the chamber is kept dry. Solvent or oil in the chamber will cause symptoms of high pressure."

Here's the link:

Nosler - Bullets, Ammunition, Rifles, Brass, and Reloading Data.

 

[MR.SWIFT]

i believe all of the reloading manuals carry that statement

 

[Pdvdh]

Wish you would have posted that information earlier First I'd ever heard about this was in this Thread.

 

[MR.SWIFT]

was taught to me almost 40yrs ago when i started handloading anything that will make the chamber smaller be it a liquid or a dry element will raise chamber press. rule #2 in safe fireams handling be sure the barrel is clear of any obstructions this includes the chamber and what did they tell us from the black power days keep your power dry same goes with ammo

 

[Pdvdh]

was taught to me almost 40yrs ago when i started handloading anything that will make the chamber smaller be it a liquid or a dry element will raise chamber press.

Solvent, oil, or water in the chamber doesn't raised chamber pressures. They will cause false-positive symptoms of high pressure.

Notice Nosler's statement "... will cause symptoms of high pressure."

Chamber pressures are the same, wet chamber or dry. A wet cartridge-chamber interface allows the case head to impact the bolt face with somewhat greater force, and the case head brass may flow into the bolt face voids resulting in stiff bolt lift.

A smaller chamber will increase pressures. However a light film of solvent, oil, or water, doesn't decrease chamber size enough to increase chamber pressure. These symptoms of high pressure Nosler talks of are not increased pressures due to smaller chamber volume. The symptoms are caused because the reduced friction between the chamber and the cartridge with the wet interface allows for increased case head setback onto the bolt face.

 

[LapuaMile]

I realize that it has been years since this post was made, but I came across an interesting discovery this weekend, so I thought I would share.

I was shooting at a long range course, 1,000+ yards shooting both .308 as well as .338 lapua.

I had shot over 100 of my .308 rounds, loaded 175 Berger vld bullets right out to the lands, and all of a sudden I started blowing primers. I knew that my loads were precise, and this wasn't a powder issue, as I had loaded with a computerized powder trickle.

Long story short, my ammunition was wet, as it had started raining. I dried off all my cases, and ran a few dry swabs down the barrel.... Voila... No more pressure signs or blown primers.

Moral of the story.... If you are already shooting a slitly hot load, with bullet seated out to the lands, the additional water on the case creates major pressure increases. Postulate that this is either due to the volume of air that the water displaces, or maybe the water drops heat so fast that they turn to steam, next creating a mini pressure cooker. Either way, I was skeptical until I dried things out and the problem vanished.

I hope this helps anyone who has struggled with this mystery.

 

[Eaglet]

Still the above explanation is right-on. Water does act as a lubricant.

 

[T3-OleMan]

After rereading all 14 pages of this again, since it was just reactivated, I thought I'd post my March post about super polished brass causing extractor marks and wondering if I was too close to the edge!


There were some very good replys pointing to other papers on this subject. Enjoy and have a nice day.


http://www.longrangehunting.com/for...brass-cause-excessive-stress-bolt-face-69576/


Now, however, Nellie has discovered 185 GMXs at 3,080 fps and is all "hot & bothered". If she is happy, I am happy, so I will just use the factory Superformance this season and pray it is as good an ELK killer as the Barnes TTSX and MRX hand load 185s & factory 225s.

Good Luck to ALL - and be safe out there.

 

[paphil]

With heat and pressure, water turns to steam and increases pressure. Just ask any tree that has been struck by lightening !! Also I noticed pharworths chronograph speeds through two chronographs were different for the soapy bullet. Probably was so slick that it defied friction with the air and just kept going faster. I loved those pictures, really got a good laugh out of them !!