Moving the front sight when you shorten the barrel is an easy job—if you've got the right tools. Let me show you how to do that using simple hand tools and a special fixture.
The special fixture we're using is from Wheeler Engineering. First, you'll need to mark the desired barrel length. Then, drive out the front sight from left to right using a brass punch to protect the sight.

Next, level the barrel using the steel block and bubble level provided by the kit. Now we'll need to clamp on the cutting fixture, keeping it level as well.

Start with a mill bastard file, using the edge to cut the center of the new dovetail.

The kit includes a 60-degree safe-sided file for filing out the corners of the dovetail. Using a bit of chalk will help prevent the file from loading up with metal filings. File just to the edge of the fixture, then remove it and check for fit. Lastly, a bit of oil will prevent galling as you drive in the front sight. Now we're ready to cut the barrel to length and recrown it.

The right tools, a special fixture, a little bit of knowledge, and some patience—that's all it takes.
-- Larry Potterfield