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/LongRangeMoose]

I think technically you could still but a 50BMG. Aslong as the barrel was short enough to he under the Joule limit?