Honestly, this is a friend's experience, so my ability to answer to further details may not be complete:

.30-378 Weatherby. Handloads of IMR7828 powder and Federal Magnum primers. (unk bullet, but can supply that later if it matters).

These loaded about 15 years ago, stored cool and dry.

More than one of these loads failed to ignite, and when that happened, bullet lodged in throat. (Happily all came to screeching halt, bullet was extracted.)

Here's something I don't know about, but perhaps it is common: Powder in the case had been transformed to cured concrete. (The friend insists that after the first misfire, he rattled each cartridge before firing, and they all exhibited sounds of a normal charge of powder, then after misfire the "concrete" consistency was observed)

I suspect contaminated or moisture-affected powder, but all storage was as it should be. I'm also skeptical about the concrete phenomenon occurring AFTER the primer ignited. But, my friend has been loading and shooting longer than I have (50 years).

Anybody seen this before? Speculation has been done already by three of us, so no more of that needed. Need someone with firsthand observation of this and probable cause. Again, I may NOT have the "whole story" here.

Thanks.

I would suspect the powder either got moist before loading or during storage. I have stored ammo for long periods with no ill effects as long as it is dry and temperatures change too much too fast. Killed an elk this year with shells loaded in 2000.

My FIL is still shooting 8mm/06 loads his father loaded back in the 60’s

They all still go boom.

Primers were not sealed or batch of bad primers would be my guess.

I bet that was a bit disconcerting

Okay, so maybe this isn't common or seen (much) before. I know from personal experience not to have any concerns firing ammo loaded many, many years ago as long as it has been stored correctly. I also have experience with old primers doing all sorts of weird stuff.

Leaning toward powder contamination in this instance.

Still would like to hear from someone with firsthand knowledge of this "concrete" phenomena (even from a round dismantled rather than "fired").

The Mystery Train rolls on....

Have you pulled a bullet to see if all the powder is caked? Since it holds so much powder maybe 50% of it is caked and yet you can hear the powder moving arouind.

Good point, will convey that to the buddy. But as he described it, the "concrete" happened as a result of igniting the primer, and was absolute on all the powder inside (after it rattled fine prior). I can't see how that occurs. Of course, the solution is to dismantle all completely to brass and begin anew.

Thinking if the primer ignited with enough force to send bullet into barrel, powder is bad.

Yep, same thing happens when the case is not charged with powder. Or so I hear.