Whats to cutting a dovetail??. You lay the lines out on the barrel with a scribe, measuring twice and cutting once. Use a hacksaw to cut between the lines, a series of cuts to remove as much metal between the lines as possible with the saw. Then, use a coarse file to hog out the rest of the metal. Then use a fine file to dress the edges to the exact width of the of the slot. ( most people leave this step until they cut the angles with a triangle shaped file, usually using one that has the teeth ground off of it on one side, so you don't remove more metal from the bottom of the slot while cutting in the angled dovetails.)
You also mark the angles on the barrel. Prussian blue, or any other metal dye can be used to aid you in seeing the lines while working. You want to take your time and fit the sight to the dovetail as you get down to the final few strokes of your files.
The depth of the cut for a dovetail slot should be no more than 1/2 the thickness of the barrel between the bore and the exterior. YOu want to leave at least .020" inch between the bore and the bottom of the cut for safety, and more if you can.
The dovetails on the sights sold are often much deeper(longer?) than necessary. If you are going to remove metal from anything, take it off the bottom of the dovetail on the sight. Take a look at any .45 Colt 1911 pistol to see how short the dovetails can be to keep a sight on your barrel, for a reference.
If there is any error seen with hobbyist work on dovetails, is that they cut them way too deep, never considering that the manufacturer is giving you all that extra metal to suit the " cannon " you want to put the sight on. :thumbsup:
