Long string load development

[MattPeetz]

I don't understand why oil or headspace would cause it. It takes pressure to make the brass flow into the ejector hole. Seems easy to understand to me. Head space and oil don't increase the pressure. Cannot find reloading data for his powder and bullet to see how close he is to max. Can someone quote the book data to compare.

Ok. Go ahead and oil up your chamber and shoot it then.
If your case can’t grab ahold of the chamber wall when fired( which it does) it slams back into the bolt face thus flowing into ejector hole thus thinking it’s pressure.
Hell, just put some water on your cases with a known ok load and fire it. You will trash that case.
So that load has to much pressure and the load is to hot?

To much headspace is the same. It slams into the bolt face before sticking to chamber.

 

[Jager]

I don't understand why oil or headspace would cause it. It takes pressure to make the brass flow into the ejector hole. Seems easy to understand to me. Head space and oil don't increase the pressure. Cannot find reloading data for his powder and bullet to see how close he is to max. Can someone quote the book data to compare.

Lyman has that bullet/powder maxing out at 37.5gr, producing 62K psi in a 24" universal receiver. QuickLoad has the stated 37.3/IMR-4166 producing 50K psi - but that's without several important data points (case volume, bullet seating depth, chrono results, etc.), so that model is of questionable value until you have those inputs.

Clearly, it was a pressure-related event. But it was also clearly temperature related. Reducing the load might very well be the answer. But that doesn't really address the original question.

Knowing what pressures were being generated by the load - as developed - would go a long way towards illuminating how much safety margin exists.

 

[Bc'z]

Lyman has that bullet/powder maxing out at 37.5gr, producing 62K psi in a 24" universal receiver. QuickLoad has the stated 37.3/IMR-4166 producing 50K psi - but that's without several important data points (case volume, bullet seating depth, chrono results, etc.), so that model is of questionable value until you have those inputs.

Clearly, it was a pressure-related event. But it was also clearly temperature related. Reducing the load might very well be the answer. But that doesn't really address the original question.

Knowing what pressures were being generated by the load - as developed - would go a long way towards illuminating how much safety margin exists.

Hodgdon lists 38gr max with Sierra 123, fed 210m, hornady brass.

During initial load development I was running a .288 bushing, a week prior I ran a bushing test, .286 bushing shrank group considerably, this is giving me 4.5-5 thousandths tension.
Lack of time kept me from any further load work and testing
Thoughts?

Velocity for load tested during seating test was 2880 average
28" 8 twist Hawk Hill.

 

[BartsBullets]

Shooting a club match yesterday I noticed a sharper recoil ,and ejector mark on round 7 of 20 not counting sighters.
Agian in the 2nd relay I started getting ejector Mark's halfway through the string. Temps were high 90's.
When doing load work temps were in mid to high 80's letting barrel cool between every 6 shots.

So my question is.
Should I be shooting continuous when doing initial charge weight to simulate heat generated during long strings of fire to find preasure caused by heat?
Cartridge and load..
6.5 Creedmoor
Peterson brass, cci200,
37.3gr IMR4166, 123gr scenar

You were just too hot (on your load).

Bart

 

[Webster]

Ok. Go ahead and oil up your chamber and shoot it then.
If your case can’t grab ahold of the chamber wall when fired( which it does) it slams back into the bolt face thus flowing into ejector hole this thinking it’s pressure.
Hell, just put some water on your cases with a known ok load and fire it. You will trash that case.
So that load has to much pressure and the load is to hot?

To much headspace is the same. It slams into the bolt face before sticking to chamber.

Maybe you will believe Bart. Slamming back does not increase the peak pressure.

 

[Jager]

Hodgdon lists 38gr max with Sierra 123, fed 210m, hornady brass.

During initial load development I was running a .288 bushing, a week prior I ran a bushing test, .286 bushing shrank group considerably, this is giving me 4.5-5 thousandths tension.
Lack of time kept me from any further load work and testing
Thoughts?

Velocity for load tested during seating test was 2880 average
28" 8 twist Hawk Hill.

2880 is hot. That's the velocity Lyman got, using the Scenar, at their max pressure of 62K.

In contrast, QL is only predicting 2593 fps / 50K psi at your 37.3 charge weight. To get QL to predict 2881 fps (at nearly 70K psi, 8K over SAAMI max) requires 41.7gr of 4166, with a 102.2% charge density. Were you running a compressed charge?

My guess is your brass has significantly less volume capacity than the 51.5gr that QL has as its default. And the increased neck tension from the smaller bushing would also have bumped your chamber pressure.

The bottom line, everything else aside, is that 2880 with that bullet and that powder is hot. Throw some extra heat into the mix and it's not surprising you experienced what you did.

 

[Bc'z]

2880 is hot. That's the velocity Lyman got, using the Scenar, at their max pressure of 62K.

In contrast, QL is only predicting 2593 fps / 50K psi at your 37.3 charge weight. To get QL to predict 2881 fps (at nearly 70K psi, 8K over SAAMI max) requires 41.7gr of 4166, with a 102.2% charge density. Were you running a compressed charge?

My guess is your brass has significantly less volume capacity than the 51.5gr that QL has as its default. And the increased neck tension from the smaller bushing would also have bumped your chamber pressure.

The bottom line, everything else aside, is that 2880 with that bullet and that powder is hot. Throw some extra heat into the mix and it's not surprising you experienced what you did.

Thanks for the input
I'm thinking I'll re-shoot charge weight from 35.5-37 gr. Keeping all other aspects of load the same with no cool down period.

 

[dthomas]

Peterson brass is thicker than most other brands you will usually have to drop your charge weight some.

 

[MattPeetz]

Maybe you will believe Bart. Slamming back does not increase the peak pressure.

Maybe instead of being a interweb know it all, you will go try what I said and see the results. You might learn something.

 

[MattPeetz]

Maybe you will believe Bart. Slamming back does not increase the peak pressure.

And if you re read what I wrote. I said nothing about his load. I am telling you that your blanket statement is not correct. It’s ok to be hurt hurt.

 

[wagonman]

Peterson brass is thicker than most other brands you will usually have to drop your charge weight some.

they state this on their website I remember reading it

 

[Bill Norris]

I have had to reduce any load that I placed in Peterson brass in my 260AI.

 

[wagonman]

I have had to reduce any load that I placed in Peterson brass in my 260AI.

likewise in my 260ai also

 

[JFrank]

You were just too hot (on your load).

Bart

@Bc'z This is my first thought also.

 

[JMayo]

I don't understand the "shoot them as hot as you can"
I find nodes not at the max ....

Sometimes the "gallery here" sounds like a bunch of kids just wanting to talk guns.

 

[Dgd6mm]

Peterson brass is thicker than most other brands you will usually have to drop your charge weight some.

 

[Dgd6mm]

Extractor marks are not only caused by high pressure.
So much can cause that. To much headspace, oily chamber etc…..

Matt is still correct on this. I'd check the H2O capacity of the brass.

 

[338 Mollett]

Some powders burn cleaner than others.Some of them need more pressure to burn cleaner. After you jb the throat I think you get a good idea of what is going on.

 

[Kracken McGraw]

It will be interesting to see if you have any carbon in throat. But with your round count, caliber, and your current cleaning regimen it doesn’t sound possible.

 

[Bc'z]

It will be interesting to see if you have any carbon in throat. But with your round count, caliber, and your current cleaning regimen it doesn’t sound possible.

I decided I'm going to take it over to Skaggs and look for a carbon ring before scrubbing.
Going to take a couple length measurements also.
Loaded round neck measured .2905
Fired .2940.
I share tuning strategies with a couple BR shooters, but they're not running as many rounds.
I agree with @BartsBullets that I'm too hot, and need to search out the lower node.
2nd relay it shot great with a
199-14X but showed preasure from the extreme demand of long string and conditions.
Back to the drawing board. Lol