Been reloading for over 30 years but never saw this before.

About 17-18 years ago I loaded up the following in .357 Mag all with new unfired Remignton brass & CCI 550 primers:
50 rounds with 140 gr XTP's, 17.5 grs. of Win 296
50 rounds with158 Gr. XTP's, 15 grs. of Win 296
50 rounds with 180 gr. XTP's, 13 grs. of Win 296

I put them in new plastic ammo cases. They sat in the closet I use with all my other powder, primers, brass, and ammo until now. Stable environment. No excessive heat, cold or dampness.

Bought a new Taurus 605 for concealed carry and decided to shoot them in it.

First 5 rounds of each loading had at least 2 full case splits lengthwise! The 180's had 4!!!! I was stunned.

I wanted to save the brass and bullets figuring the loads were too hot. Used an RCBS collet puller to pull all the bullets, and dumped the powder, which appeared to be fine.

I then resized the brass.

However, when I belled the mouth, 32 of the remaining135 split lengthwise from the rim like when fired! Huh???

I was belling the mouths as little as possible as I never like overworking brass. It took little pressure to split the case and I could feel them split through the handle of my Lee single stage press. They split before belling even a bit.

Keep in mind these 32 of 135 had never been fired!

These were new brass with no corrosion. They looked fine with very minor tarnishing.

What happened to make this brass so brittle? I have lots of other brass in that closet and some is as old and they are fine.

I've heard a theory that brass can get brittle over time just from sitting around. How exactly that works or makes sense sure beats the heck out of me! Hope your cylinder walls didn't get damaged.

My cylinder walls have no damage.

I had some factory round I fired after with no issues.

That is strange ,, what case lube did you use ?
Is it possible that reacted with brass over time , and made brass brittle ?

No lube.

Carbide dies

Several runs of Remington brass had annealing issues. One of the reasons I quit using it.

Could it be a bad batch of brass?
Maybe there was a recall on it , that you may have missed?

since you had new never shot cases that cracked when pulled I suspect a load of bad brass.

Either the loads were too hot or you got a bad batch of brass...

The only other thing I can think of would be the chambers on your Taurus would be over spec size... Possible but highly unlikely.

You said it was new brass, and it's been almost 20 years, but had you shot these powder/bullet combos before?

I'm leaning towards a bad batch of brass. I've experienced it myself.

Mike

Mike-in A-town.

135 were never fired. Pulled the bullets. Resized. Then they split when belling the mouth.

Consensus seems to be bad brass. Could’ve been a recall I never heard about.

Thanks for the replies.

I agree bad brass is probably the most likely cause.

Mike

brass got brittle from something, and it doesn't take much to do it, had the same problem with brass that I left set for several years. could be anything, a battery close by, an open can of comet/ajax, anything!

Possibly brittle brass not annealed properly or a defect in the sizing die that causes a deep scratch or cut on the brass.

just bad brass, shoot it, dump it and move forward.