No pressure signs last week-Over pressure today

[Copen1822]

I'm working up a load for my 6.5 Creedmoor (12LRP) and ran into some issues today.

Load specs are Berger 130 VLD, new Hornady brass, RE-15, CCI 200, 2.202"CBTO (.020" jump)

Last week I shot loads from 36.8gr to 39gr with good results and only saw a very faint ejector mark on one of the cases of the 39gr load. So I load up 20rds @ 38.5gr to play with today and I'm getting heavy bolt lift, flat primers, and super bad ejector marks. I shot three rounds to confirm and they all look the same so I called it quits.

These rounds are identical to the 38.5gr load I shot last time. I pulled bullets when I got home and the charge weighed 38.5gr. OAL is the same. The only thing I did to the rifle was clean it. The cases seemed to have a lot of oil on them after extraction, not sure if that could be an issue. Cases are new and I didn't size them, just ran the mouth through the expander ball to correct any case mouth deformities. I'm only working with RE-15 because I can't find anything else. There is not much data for RE-15 and the Creed but Hornady lists 39.2gr max with their 129gr bullets. The temps were in the low 60's both days. It was raining today, clear last trip.

Any ideas on why I'm seeing this? I've been reloading for a little over a year for .308 and .243 so I'm far from experienced at this. I'll take any help I can get.

 

[Copen1822]

Anyone.....?

 

[JRM83]

I haven't been shooting or reloading very long, so if I'm talking out my ass hopefully someone more experienced can set me straight.

When a round is fired the pressure inside the case forces the brass to expand against the walls of the chamber, and the grip of the case on the chamber walls prevents the case from moving. When the pressure drops the case shrinks a bit and the case is no longer pushed tight against the chamber walls allowing it to be extracted. If there is oil in the chamber, or the outside of the case, when the round is fired then the case will not be able to grip the chamber walls as tightly when the brass expands and the case will be forced back into the bolt face. This will cause the primer to flatten on the bolt face (possibly flowing into the firing pin hole) and the ejector will be forced hard against the case head leaving heavy marks.

Try making sure the chamber is clean and dry and there is no lube/oil on the cases.

 

[Dogtown]

Yeah, my first thought was "he's shooting RE15 in different temps", but that's obviously not the case. Too much oil in the chamber could be the problem, because it's an incompressible fluid (unlike air) and will push back against the brass as it expands to fit the chamber. It could be that this has created just enough added pressure to give you a spike. Clean out your throat and chamber and make sure they're dry and free of any particles, then load them up and try again.

 

[Dan Newberry]

I haven't seen Hornady's data... but that looks like it's on the extreme liberal side.

Hodgdon shows, with 4064, Varget, and W749--all powders that burn about like RL15--much lower maximums. They're showing about 35 grains as max with 130's in the Creedmore.

With many powders, you'll find oddities occurring like what you have seen when the powder charge is too high. It'll work one day... and then some change of one sort or another and you end up in primer-puke city.

Your data looks more like it's for 120 grain bullets, rather than the 130's you're shooting.

Back it down and work it back up from around 33 grains, heading toward 35 grains in .3 grain increments and you'll find a safe, useable node.

Dan

 

[PCR]

You say the cases had a lot of oil on them when you extract them. Is it oil? How much and how did it get in the chamber. Did you mop out the chamber and bore when you got home?

 

[boone3380]

I haven't seen Hornady's data... but that looks like it's on the extreme liberal side.

Hodgdon shows, with 4064, Varget, and W749--all powders that burn about like RL15--much lower maximums. They're showing about 35 grains as max with 130's in the Creedmore.

With many powders, you'll find oddities occurring like what you have seen when the powder charge is too high. It'll work one day... and then some change of one sort or another and you end up in primer-puke city.

Your data looks more like it's for 120 grain bullets, rather than the 130's you're shooting.

Back it down and work it back up from around 33 grains, heading toward 35 grains in .3 grain increments and you'll find a safe, useable node.

Dan

I'd go with this, probably tough to find a more knowledgeable person on the subject.

 

[diego-ted]

I haven't seen Hornady's data... but that looks like it's on the extreme liberal side.

Hodgdon shows, with 4064, Varget, and W749--all powders that burn about like RL15--much lower maximums. They're showing about 35 grains as max with 130's in the Creedmore.

With many powders, you'll find oddities occurring like what you have seen when the powder charge is too high. It'll work one day... and then some change of one sort or another and you end up in primer-puke city.

Your data looks more like it's for 120 grain bullets, rather than the 130's you're shooting.

Back it down and work it back up from around 33 grains, heading toward 35 grains in .3 grain increments and you'll find a safe, useable node.

Dan

OCW Dan Newberry? It's an honor to have you here providing insight!

thx TEd

 

[former naval person]

Clean, degrease and dry the chamber and refire and report.

 

[demolitionman]

You gotta get that case lube entirely off the cases before you fire them, or you'll end up with slick chamber walls like FNP said.

 

[melloyello]

When you cleaned your rifle how much oil did you leave in there? I don't ever leave any oil unless I plan on storing it for a while. When I say a while, I mean a year. Nothing wrong with using some oil after using a bore cleaner but get all of it out that you can before you shoot it. Even if you think you got it all out there will be a thin film and that's okay. My guns stay in my safe when not in use where I can control the moisture. And if they have oil in them I clean it all out before I shoot them. As stated before oil doesn't compress. It's not good in the chamber or the barrel. It can create more pressure and oil attracts dirt.
Out of the 15 or so guns I have only 2 of them have oil in the barrel.

 

[DroidSniper]

Dan Newberry is legit. Using his OCW method got my win mag shooting into 1/3 MOA.

 

[Copen1822]

Thanks for all the info guys. Good stuff. I don't know what happened with the oily chamber, I use oil very sparingly but there was definitely a film on the extracted cases. I can't get out this weekend because I'm on call, but I will post my findings after I shoot again. Thanks again.

 

[Temp9]

From a study conducted by the US Army regarding failures of their M249 SAW's:

"Lubrication in Chamber can increase bolt face load an additional 2000 lbs (μ=0.05), 3000 lbs (μ near zero)"

http://www.dtic.mil/ndia/2011ballistics/11826.pdf

 

[DroidSniper]

From a study conducted by the US Army regarding failures of their M249 SAW's:

"Lubrication in Chamber can increase bolt face load an additional 2000 lbs (μ=0.05), 3000 lbs (μ near zero)"

http://www.dtic.mil/ndia/2011ballistics/11826.pdf

Awesome link.

 

[Dan Newberry]

And being 4 grains over max increases pressure a bit as well...

 

[Dan Newberry]

okay just razzin' a bit about the 4 grains, though by Hodgdon's comparable burn rate powders you're about that much over their max. I'd say you'd be fine just backing it down a grain and a half to two grains, and working to find the node in that area. Data is still sketchy on this cartridge, and lots of publishers are waiting to see what others do before sticking their necks out so to speak.

 

[boone3380]

I've heard of several bolt shooters that lube there cases before they fire them. They said they get longer brass life using lube.

 

[Temp9]

I've heard of several bolt shooters that lube there cases before they fire them. They said they get longer brass life using lube.

You're less likely to get case head separations if the case is lubed, but of course, you'll see pressure signs a bit sooner.

 

[X-fan]

And being 4 grains over max increases pressure a bit as well...

Roger that!
Throw in a decent temperature change and "Huston? We have a problem!"

 

[X-fan]

I've heard of several bolt shooters that lube there cases before they fire them. They said they get longer brass life using lube.

Stupid is as stupid does.

 

[Edo1]

You're less likely to get case head separations if the case is lubed, but of course, you'll see pressure signs a bit sooner.

Really? Explain how your theory on this is true?

 

[Temp9]

Case head separation occurs when the brass is at the forward extent of the headspace. When the primer pops and the powder begins to burn, the casing expands and grips the chamber. The rear part of the brass will stretch (in the case head area) rearward until it contacts the bolt face. This accounts for the rearward bolt force. If the chamber is lubed, however, the casing won't be able to grip the chamber to the same extent. Instead of a rearward stretch, you get a rearward shift of the entire casing, along with a whole lot of additional bolt force. Someone did an excellent write-up of this, but I can't find it now. As I understand, many people recommend the use of lube on the case when fireforming brass for this very reason.

Since I've never tested this, I can't say if it's completely true, but that's my understanding.

 

[Copen1822]

Update:
I made it back out today and found a decent load with 36.5gr RE-15. Started to see some flatter primers at 37.6 and stopped. I believe Dan was right and I was just over pressure with
my 38.5gr load, I'm still not sure why I didn't see any pressure signs the first time out. Best news is I finally found some H4350 today, so I think my experimentation with RE-15 is over.

Thanks for the help.

 

[Dan Newberry]

I'm glad you got things sorted out. The H4350 is more or less "mother's milk" for the 6.5CM... though other powders can certainly do well, I think with the 140's the 4350 burn area will give the most speed safely.

We are seeing some fantastic performance from Berger's 130 grain Target VLD's in this chambering. IMR 4064 works very well with those.

In times past, I've had loads pressure-up on me and give me a nasty surprise. Back when I used to want to "drive it like I stole it" this was more common than it should have been... Lots of powders can exhibit the behavior you saw: fine one day, primer puke the next. The temperature, atmospheric conditions, etc., can easily put a load which was "on the verge" over the top.

Superformance powder can be useful in this cartridge, and I would think Hornady would give you some ideas along that line, if or when you ever may want to try that powder.

But that said...

I'm going to remain an "old school" powder guy until this new breed of "super powders" has been fully tested by the "hold my beer and watch this" crowd.

Dan

 

[former naval person]

The National Armory produced some bullets back in the 30's that were tin (I believe) plated. The match folks took to greasing the bullets lightly. Then too much. The grease got on the chamber walls and some of the '03's came apart. They stopped the practice. Looks like we are reinventing the (square) wheel.