A tale of two sets of brass...

[clcustom1911]

Prime 6.5 Creedmoor Brass, 4th firing, 147 ELDm @ 2730-ish (beyond SAAMI velocities)

Set #1: moving quickly toward case head separation.

Set #2: still doing well.

What am I gonna do about it? Chuck the bad ones, drop my load down to 2600 FPS to get more firings out of the brass

 

[gigamortis]

What is happening in your pics is typical of brass in which the shoulders have started out bumped back too far for the chamber, or too long of a headspace dimension in your rifle. When fired, the brass does most of its stretching just above the case head junction to fit the headspace of the chamber . Eventually it will get too thin there and a case head separation can happen. Have you bumped shoulders somewhere during the life of those 4th fired ones? I use a paper clip bent with a 90 degree hook on the end to feel for any step downs in thickness just above the extractor grooves on brass that I have resized a few times. You will be able to feel a step down in thickness on the inside long before you see any evidence on the outside of the case like you have in your pics.

During my junior reloading days, I was foolishly "controlling" my shoulder bump by raising my sizing die away from the shell holder a few thousandths. If I had more case lube than normal, the shoulders would get bumped back more than necessary. After a few bump regimens on the same brass, I was seeing what you have in your pics. My case wall thinning was caused by shoulders being bumped too far back and getting stretched back out on the next firing.

I have since wised up and gone to a Redding body die and the Redding competition shell holder set. With this system, you can set the die depth to where positive contact is always made with the top surface of any of the shell holders. This provides a repeatable hard stop for every case that goes up into the die regardless of case lube variation or press flex. The 5 piece competition shell holder set has holders that vary in their lower pocket depth in increments of .002" from +.002" to + .010" so that you can precisely control how much of the casing goes up into the die. For my chamber and sizing die combo, I use a +.008 shell holder to give me .002" shoulder bump when my bolt lift starts getting a little sticky. I haven't had any more thinning in my case walls for the life of any batch of brass since.

 

[clcustom1911]

Oh, trust me, I know I'm bumping my shoulders back too far with my lasy cycle of using my super fancy shmancy Lee Precision full length sizing die (a bit of sarcasm there). I just don't want to buy the Redding setup because, while it is clearly superior to my setup, I'm deploying soon (like 3 weeks) and won't have time to get it, set it up, tune it, shoot with setup, etc.

 

[ShtrRdy]

You should still be able to limit the amount of shoulder set back using your Lee die. Just don't screw it in as far.

It's probably best to not use the cases which are about to spring a leak.

I dont think 2730 is too far out of line. Let's see what others have to say.

 

[Steel head]

Oh, trust me, I know I'm bumping my shoulders back too far with my lasy cycle of using my super fancy shmancy Lee Precision full length sizing die (a bit of sarcasm there). I just don't want to buy the Redding setup because, while it is clearly superior to my setup, I'm deploying soon (like 3 weeks) and won't have time to get it, set it up, tune it, shoot with setup, etc.

When you get back look into a lee collet and Redding body die.
For the money it can’t be beat.
For a lot more money it’s still often superior.

 

[clcustom1911]

When you get back look into a lee collet and Redding body die.
For the money it can’t be beat.
For a lot more money it’s still often superior.

I have the collet die. Its excellent.

 

[Geno C.]

That ring could have been caused by the first firing of the cases were too small when they were new.

 

[clcustom1911]

That ring could have been caused by the first firing of the cases were too small when they were new.

True, but with this particular set of brass, when I made the rounds, there were no rings present, after firing, the rings appeared.

 

[Huskydriver]

Curious...the ring looks a tad high. Do you put your cases primer up in your reloading box after you shoot?

Have you cut a case in half to see how deep the stretch is yet?

 

[clcustom1911]

Curious...the ring looks a tad high. Do you put your cases primer up in your reloading box after you shoot?

Have you cut a case in half to see how deep the stretch is yet?

Cases went into a styrofoam tray into cardboard ammo box.

No I haven't performed a post-mortem yet.

 

[gigamortis]

Check you 1x and 2x fired brass with the paper clip feeler down the inside wall even though you may not see any evidence on the outside. If you feel a reduction in thickness on your 1x brass, that would point toward shoulders too short right out of the gate for you chamber.

 

[clcustom1911]

Will do. Thanks

 

[Huskydriver]

Cases went into a styrofoam tray into cardboard ammo box.

No I haven't performed a post-mortem yet.

I have noticed my ammo boxes put a ring right there if they get rattled around in the back of the Jeep looks like the ring of death but it's just from the brass rubbing the cells in the box but if your putting them in styrofoam that rules that out.

I use a straight dental tool that I have put a sight hook on the end of instead of a paperclip but the paperclip works fine too.

Sometimes this isnt sufficient to guage how far the damage has progressed so like you said I autopsy one of the suspect ones so I can tell if it's time to scrap the lot or if it's good to go another loading.

If it is close to failing, I suspect to big a push back on the first reload

 

[sam4886]

It is worth cutting one open to check for sure. I'm running 2745 fps with 143s on hornady brass with my 6.5 creed and I'm at over 10 firings and they look very similar to yours. Like mentioned above, I'm sure most of mine is caused by rubbing in the ammo box as I have no signs of weakened brass.

Are they different lots or something? I suppose that could cause an issue....

 

[clcustom1911]

Post-mortem dissection complete. Had to soak in MPro7 to get layers of carbon off.

*I think* the shoulders were pushed back too much on the last loading of this brass because I switched from my single stage press to my Dillon 450 and the Dillon shell holder is probably thinner than my standard shell holder, allowing the case to be pushed up higher into the die, therefore knocking the shoulder back too much.... like a lot too much LOL......

Fuck ?

 

[clcustom1911]

HOLY SHIT. I just measured the shell holder depth! I'm only knocking the shoulder back another 0.007" FUCK

My Lee shell holder depth....

Dillon:

 

[Huskydriver]

Post-mortem dissection complete. Had to soak in MPro7 to get layers of carbon off.

*I think* the shoulders were pushed back too much on the last loading of this brass because I switched from my single stage press to my Dillon 450 and the Dillon shell holder is probably thinner than my standard shell holder, allowing the case to be pushed up higher into the die, therefore knocking the shoulder back too much.... like a lot too much LOL......



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Fuck ?

Comparators are your friend homie... But yes I would say that lot is toast. Always check your die set up each time you reinstall it for proper bump ?. Lesson learned...

 

[clcustom1911]

Lesson learned...

Yup. Lesson learned the $$$ way. Fuck.

 

[sam4886]

Ouch. Did you at least get in on that midway deal for 250 casses for $100 a while back?

 

[clcustom1911]

Nah, this was my Prime brass I got when I bought some cases of 6.5 Creedmoor from Prime when they were originally selling a couple years back.

 

[gigamortis]

Good to see a logical answer to the issue.

 

[Kadams1563]

Fix?

Buy CO-AX
Buy comparator