Overuse of black malt?

I just finished brewing a 5 gallon extract batch and I think I may have used too much black malt 500 L (aka black patent). I somehow thought black malt was similar to roasted barley and now realize that they aren't interchangeable. I used 12 oz. of black malt, 4 oz. of english crystal 55 L, 6 lbs. light LME, 8 oz. lactose, 6 oz. molasses, and 1 oz. fuggles for boiling. Any thoughts on this?

Just read a couple threads on black malts and it looks like 10% is the maximum you want to use for the grain bill. I might be close to the 10% or I may have made the blackest harshest tasting beer in Sacramento.

Did some calculations and it appears that the black malt makes up a little over 11% of the grain bill (1 lbs. LME equals 1.25 lbs. 2 row grain).

I think I may be in the clear with this one.

I just got a recipe from tastybrew.com for a clone of Deshutes Brewery's Obsidian Stout that calls for :
8.5lb. LME
1 lb. Crystal malt (80)
1 lb. Ghocolate malt
.75 lb. Roasted Barley
.75 lb. Black Patent
2 oz. Perle@60 min.
Safale 04 yeast
This is my next batch to brew

While they are not interchangeable, roasted barley and black patent can be used in about the same proportions. For porters you want black patent, and for stouts roasted barley. The general rule for the highly roasted malts is about 10%. You should be okay by the grain bill.

At first I thought you were going to say some insane amount like 5 lbs used in a recipe, but 12 oz is just fine.

Willy, that's funny that you mentioned that recipe from Deschutes Brewery, I was actually really impressed with their Abyss Imperial Stout and wanted a lighter version of that brew. I'll have to check out their Obsidian Stout, they've got some real full bodied complex brews.

I'm real happy that my brew isn't going to be 5 gallons of liquefied coal.

As the others have mentioned you'll be just fine with that amount. You'll need a little bit of extra aging time I think as the taste is much more acrid than roasted barley. But as long as you're aware of that I think you'll have a great beer on your hands in 3 months or so.