What’s the largest caliber rifle that’s available in the open market?

[u/meowmixonroids]

I was scrolling through Reddit earlier and came across a historical post featuring a Boys anti-tank rifle. It got me wondering:
What's the largest caliber rifle you personally own?
And out of curiosity, what's the largest caliber rifle that's currently available on the market?
Looking forward to seeing everyone's answers and maybe a few pictures too.

Cheers

[u/RealTurbulentMoose]

I looked up a .500 Jeffery I saw used the other day and that’s getting over 9000 joules if you load it up.

Why wouldn’t you?

Also, possibly why it was available used. Someone probably took it out one time or on safari or something and said never again.