[Redbob]

"My guess is that a cartridge in a fire would behave like a mini hand grenade, with a range of a few feet or so."

You guess wrong; see other replies.

[Leaning Right]

I’ve looked around a bit more since my previous post. A number of sources say that the brass often fragments into small, flying pieces. So I think I’ll stand behind my “mini hand grenade” comment.

The key word here is “mini”. The pieces of brass - if any - would be small and light.

[depressed in 06]

I had a .30 cal round go off before it could chamber in a M1. Powder was everywhere. The bolt struck the primer making the round go off. Primers are pretty noisy and can by themselves get bullets stuck in the barrel.