Many years ago I studied in the shop of Ron Ehlert. He showed me a pretty foolproof way to get wedges installed. After doing a very CAREFUL layout on the outside of the forearm of where the underlugs were in the barrel channel he used a 1/16" bit to drill through the stock and lug a couple of times. He removed the barrel. Using a piece of 12" steel flat stock, one end of which was ground and filed about 4" to the exact size of the wedge, he heated up the steel piece cherry red and burned his way through the forearm area from both sides of the stock. Then he cleaned up the stock slot with a small file. Made it a perfect fit. There was some scorching of the wood but he did all this prior to any shaping of the forarm.
He then parked the barrel in his drill and used an end mill to open up the lug for the wedge.