According to what i've read, the .50 caliber BMG (Browning Machine Gun) was developed in 1910 and went into full service in 1921.  You can find ammo in regular ball, tracer, armor-piercing (AP), incendiary, and saboted sub-caliber rounds.

It can also be used as an anti-materiel rifles (AMR), designed for use against military equipment, structures, and other hardware (materiel) targets. They are employed to eliminate equipment such as engines and unarmored or lightly armored targets.

They have been used as anti-aircraft defensive weapons, but they've been found less than capable in that role. They can, however, be effective against stationary aircraft similar to any other mechanized equipment.

I think what alarmed the TSA is the extreme appearance of the round.  Even though it's within the caliber limits set by TSA, the sheer size and weight is massive compared to common self defense rounds.

Yep.  Stacked side by side it even makes the 30-06 look puny.  I hated cleaning the Ma Duece after training with it.  All the parts were heavy and you get super oily, dirty, and tired after cleaning it.  Just taking it off and then putting it back on the M113 was something I dreaded.

Anyway, I think the article used the term "anti-aircraft" round to fuel the fear, since it was found in a checked bag headed for the cargo bay of an airplane.  Although anti-aircraft is certainly one of the roles of this cartridge, like you mentioned it was far more effective against mechanized targets and stationary bunkers.

They could have easily said 50 caliber cartridge but it doesn't seem as scary.

years ago to a match, a TSA agent inspected my rifle and scolded me for not having it on safe. He proceeded to rack it in public view a few times and placed it in safe. He saw my orders and said I should have known better. Rifle was not loaded and not within any ammo. I cant find this requirement to have rifles with the safety engaged in their policies.

Its not a requirement.

it's not only not a requirement, but it's a stupid concept.

Why put a firearm you cleared and checked on safe -- assuming you even can?  There's no reason to.  So what if someone pulls the trigger?  It should be re-checked and pointed in a safe direction if they do that.

The entire interaction sounds like someone trying to throw his weight around and sound authoritative when he had nothing better to do.

He should have asked the passenger to verify the weapon was unloaded and cleared and never touched it himself.  if something were to happen to break at that moment, TSA would be paying for repairs/parts.  Last one to touch it broke it.

Many discussions here warn to never let anyone, especially airline staff and TSA, handle your firearms.  Tell them you'll show them anything they want, but you'll be the one doing the handling.  Regardless, it's bad policy to allow anyone other than the owner handle weapons.  What if the thing really did have a round accidentally left in the chamber, and the TSA agent causes an ND?

ummm I suppose it could've been a HE or incendiary round at one time.

That's not a round. It looks like a projectile or bullet that was dug up after 50 years.
But without a size reference in the photo, you can't even guess what the size actually is.
Kind of like a TEMU picture.

news also said the person was arrested.

That's not a round. It looks like a projectile or bullet

So is the head bullet considered ammo? No powder, primer, or brass.

Like what if someone had 1 brass casing in their bag, due to using same bag as a range bag?

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