Topping whiskey barrel off with finished beer?

I will be filling a Whiskey barrel next week with a 1.113 OG imperial stout I just brewed. The problem is, even ~5.5 gallons into the 7-gallon brewtech bucket, it clearly wasn’t enough headspace and I probably have lost approximately ½ to a full gallon of beer, I’d imagine, due to the vigorous blow-off. Never had a fermentation so crazy, even with other big beers I have done. WLP007 is a monster, I suppose (last two were cali-ale strains).

I know you want to fill the barrel to capacity, but I am quite sure I won’t get the volume at this point. On the plus side, I do have probably just shy of a gallon left of a very similar stout I brewed and is on tap currently…

My question is… Would it be fine to “top off” the barrel as-needed with the finished beer? Hopefully I don’t need more than say ½ gallon to get it full, and since the beers are so similar I wouldn’t mind at all to “dilute” the fermenting beer now. Of course, I would be careful to try and prevent any oxidation of adding the additional beer into the barrel as best as possible (bottom filling a clean/sanitized growler for example, gently pouring via funnel into barrel to top off). I was even thinking of adding a tiny bit of priming sugar before racking into the barrel (something like ½ to 1 ounce of sugar to get the yeast to scavenge any O2 for the transfer). Just as a secondary preventative, using an airlock on the barrel bung of course for aging.

Anybody have thoughts/concerns about doing this? I really don’t want to have to brew additional beer in such a small volume, so looking for an easy way to top this bad boy off.

Appreciate any suggestions and comments.

 

Well, I am thinking as long as it takes to get the flavor profile I am after. With such a small barrel ,I would expect in the area of 4-8 weeks. It just depends.

As far as the priming sugar, it would only be a minuscule amount to get the yeast active a bit. Typically for 5-gal you would use in the ballpark of 3-4oz priming sugar, I was thinking down about 1/2oz added to the primary fermenter until it kicks up again, then racking into the barrel. So by the time I do move the beer, it may already be through most of the little sugar added. Just a tactic to try and keep any oxidation risk down. Given there would be less yeast present and everything, I wouldn’t expect anything vigorous like the primary fermentation I have encountered.

Appreciate all the input everyone! Gives me things to ponder on.