Those Balcones 5 gallon barrels?

[cinderbike]

I recently bought one of the 5 gallon used whisky barrels from Balcones. My question is, are these truly 5 gallons or 20 liters (5.3 gallons). I'd prefer to fill this to the brim.

 

[StMarcos]

Probably neither of those measurements exactly. Bear in mind that you'll have top top it off regularly if you want to keep it full to the brim. Brew a bit extra and bottle/keg for topping purposes.