Curls, if you have a vertical mill there's another option...make a base to match the contour of your barrel with the holes drilled to match the crooked ones and the top and sides square with the world...matched to the rear base. Make out of crs and case harden when done. I made up a short term use cutter to do the "eyebrow" cut in the base, with the teeth hand filed. Took half an hour, including finding a chunk of drill rod close to the diameter needed and the necessary turning and heat treating. I wouldn't want to try and use it for a production run, but for a handful of bases that I needed for a similar application, it worked just fine.