Many original arms notched the bottom of the barrel to permit clearance of the lock bolt, although this was more common with larger breech sizes. In your case, since you already have the bolt located, the only options as I see them are (1) as aforementioned, dig in through the barrel channel and run the rammer hole a little deeper/more clearance. You'll only be able to do so much, though, until you run into issues with rendering a too-fat forearm. You can then patch in under the barrel, or not; it's really not necessary although over the long term it probably does add strength. (2). You can notch the lock bolt a bit, however this will mean that the bolt will need to be indexed so that it tightens down to the same position every time to ensure the notch is oriented correctly. Also you have to remember to withdraw the rammer when you loosen the bolt or you'll gouge a chunk out of it. Either approach will most likely involve a tapered inner end to the rammer, which is characteristic of pretty much most original arms anyway. Many original pieces taper down quite a bit, into the 1/4" diameter range, for this very reason. As long as you're using a good piece of hickory it should not be an issue unless you're going with a super tight patch/ball combo.
