Qwik load help requested. I BLEW ONE UP!

[lazyengineer]

I failed to get pictures posted. It has to do with my lack of computer skills. If someone wanted to volunteer to pm me there phone#, I can text them pictures to post.

At present, my best route to free image posting is to use:

postimg.cc/files

[Klem]

BR,

With your info the computer predicted max pressure is 50,232lbs. Max SAAMI pressure for the 6ARC is the same as the Grendel, 52K lbs.



This is Jager's recommended powder tweak for LT32, on the other forum.

LT-32:
1. Heat of Explosion / Potential = 3754
2. Ratio of Specific Heats = 1.2370
3. Burning Rate Factor (Ba) = 0.6545
4. Pro or Degressivity Factor a0 = 3.2400
5. Progressive Burning Limit z1 = 0.387
6. Factor b = 1.9175
7. Propellant Solid Density = 1.560
8. Load Density (calculated factor) @ 100% Fill Ratio = 0.880

Don't take this as gospel - there are a lot of tweaks here and each can confound the final result like tolerance stacking. I used Grendel as the parent case, A2015 as the parent powder, and your water filled case capacity. If you go even further and match the load density with Jager's then the peak pressure is slightly lower at 49K lbs.

If you trust that the load was OK then the case coming apart was from something else, like insipid case separation - Too much headspace. 25 reloads and that case is doing better than most, but by then even if you sneeze it will come apart.

Do you measure headspace? The difference between headspace before and after firing?

[Bat Rastard]

Thanks all, and especially Klem!

The case separated at the base.

I inspected several other cases with a paper clip. After about 20 of them I thought I found something in one of them. I sectioned the case, and I couldn't see anything because it was black in there. I tumbled the pieces and there was a shiny ring at the base. (which is where the other case came apart) I took the sectioned cases to work and examined them under magnification and found it was indeed cracking there! A co-worker, whose job it is to find cracks in metal, agreed it was cracking there.
I believe the mystery is solved!

I do measure headspace and size appropriately. That brass had only been pushed back .0015" and annealed often.

[Klem]

BR,

It sounds like what you are doing with case prep is best-practise. But as we know cases don't last forever. 25 hammer blows of 50K lbs is going to harden the case and stress it along fault lines.. Annealing is only done to the top part of the case so that won't help longevity. Sounds like the splits are occurring at the junction of the web and the case. Just normal ageing.

[Bat Rastard]

My plan is to inspect the prepped and primed cases. Those that pass inspection, will be fired one last time and retired.
I figured out the pictures!

[grayfox]

Case head separation.
20-25 loads thru a case is pushing it too far imho.

On the old guy thing, yeah lots of us in that boat too!

[Klem]

BR,

Those photos are classic case head separation. There will be a visible score mark on the chamber wall where the split concentrated all the hot gasses as it came apart. It won't affect accuracy.

Even though you are bumping the cases the bare minimum, all cases fail eventually. Seems 25-30 reloads for that brand of brass, powder, dies and loads is the max.

I would ditch the lot and buy new brass. That split was a warning. Do not use the rest of them, even one more time. If you have any loaded, pull them apart. Firing them they will be a gamble that you get the same again or worse. A bolt in your face or lose your eyesight. It's not worth it.

[Bat Rastard]

Klem, I know you are right and thank you for the concern and help.