If you have the room, a full sized barrel has several big advantages over a small (5-15 gallon) homebrew-sized barrel. The biggest is money, our barrel will cost $125 ($2.08/gal), compare that to the price of a new 5 gallon American oak barrel, $160 ($32/gal). One of the biggest problems with homebrew barrels is how quickly the wood flavor can overpower the beer, both because they are made from new oak and their high surface to volume ratio, a big used barrel avoids both of these issues.
However, using a used 60 gallon barrels is not without its difficulties. First off they are big, and once they are filled with beer it is extremely heavy (~600 lbs), you pretty much have to fill, age, and empty it in place. There is also the risk that the wood harbors bacteria or wild yeast, but that is not a big deal for a sour ale. I'm sure we will run into plenty of other issues we haven't even considered yet.
Originally we were planning to age an imperial porter in the barrel before doing a sour beer, but that plan was scrapped in the interest of avoiding the chance of 60 gallons of infected porter. A project like this can be risky as either the barrel or an infection in one person's contribution can ruin the entire batch.
We are getting the barrel (not sure of the grape type yet, but it will be a red) from Chrysalis Vineyards in Middleburg, Va. The winemaker, Curtis, was nice enough to include his services prepping the barrel right before we pick it up, so all we have to do is get the barrel in place and rack the beer into it.
Our batch will be getting its Brett/Lacto/Pedio from 10 gallons of already aged Flanders Red. According to Wild Brews adding 10% aged beer is a common way for Flanders Red brewers to inoculate their "clean" barrels. I am contributing my most recent batch, as is my friend Scott (both batches are about 5 months old). I used the dregs from Lost Abbey Red Poppy to sour mine, Scott used Roeselare Blend for his, so we should have a healthy mix of different microbes.
The Recipe - 5 gallons:
The recipe is relatively open, giving a bit of choice to each individual brewer. We wanted to get this project moving quickly, so we decided against doing a bulk grain buy and a centralized yeast propagation, both of which we will probably consider next time.
Assuming this batch tastes good in a year or so we will start thinking about what will go into the barrel next. Might be something similar, might be a big sour beer, might be something with some fruit, we will see. If the Flanders Red seems to be going well we may look into adding a bourbon barrel to the fleet to do something big, dark, and clean.