[Mr. Bird]

Uranium bombs, unlike the more complex plutonium bombs, don’t require the tricky implosion method, but can employ the simple, reliable gun method

I don't know enough about this. Are you familiar with the "gun method"?

[Cyber Liberty]

The "gun method" involves shooting a chunk of uranium through a tube and into a larger chunk of uranium, creating critical mass for the nuclear chain-reaction (fission).

The other type, the "implosion" device, uses a sphere of explosive lenses to compress a chunk of plutonium to achieve critical mass.

Both methods work. The sphere method has a more efficient yield, but the gun is simpler to design and build.

Hiroshima was a uranium gun weapon (Little Boy) and Nagasaki was a plutonium implosion weapon (Fat Man). The Trinity test explosion in New Mexico was identical to the device used over Nagasaki.