Is W231 / HP-38 heat sensitive?

[Bat Rastard]

I had a case failure today on a load I have used forever. It was hot outside, was that a factor?

[The_Shadow]

Likely a bad casing...If used it could be work hardened making it brittle, usually they split longways...
Also faster powders tend to snap the brass as pressure builds faster than slower burn rates.

[Bat Rastard]

This one blew out at the bottom.

[Ridgerunner665]

Bullet setback maybe....

[The_Shadow]

Bat Rastard, Seeing this posted in other calibers, was this in 10mm or other caliber/cartridge?

Faster powders are less forgiving than the slower ones and the pressure curve spike happens faster.
Bullet setback as mentioned can up the pressure spike...
Temps can play into pressures but we are talking placing rounds in direct sun for quite some time to raise the cartridge body temp up to near 120+ with some powders stable out to 140 degrees or more!

[Bat Rastard]

It was 9mm. 4.8 grains of powder behind a 115gr jacketed bullet. I have loaded 15k of these since the early 90s.
Three of us were sharing the gun at a GSSF match on a 95 degree day. Heat had to be a factor. I am seeing  some talk of 231 heat sensitivity online.
I am going to write it off as a fluke and attribute it to heat, possible setback on that round, and a weak case.
I am also going to buy some BE-86 to load and shoot until September or so. Then I plan to shoot up the remaining 231  loads I have already loaded. (2k or so).

Thanks for the feedback and input.

[Bat Rastard]

Update with latest(final?) theory:

The bore was filthy. I have shot many plated bullets contrary to Glocks advice. I gave the bore a thorough cleaning and the issue seems to be gone.
I think there was enough build up in the bore to cause the pressure to spike.

[my_old_glock]

Yes, increased temperatures will increase the pressure of the cartridge. If you leave ammo in the sun, you can produce very high pressures to the point of Kaboom. Most benchrest shooters keep their ammo in an ice cooler in hotter weather.   

[Bat Rastard]

Update (final):
Bad cases.  I found cracks on the bases of some of my ammo.
I found them working up a new load. New loads get extra inspection or I would not have caught it.
I have added a plunk test in a case gage on all ammo now. About 1% of my ammo wouldn't go in the gage, but would easily chamber in the barrel.
I went back and "plunked" all of my ammo and believe the issue is resolved.
Merry Xmas amigos!