Had the same problem with some laminated stocks that I bought on clearance sale. I clamped the stocks too the drill press table then chucked a router bit in the drill press. Simple at this point to route down the necessary depth. If you don't have the drill press or access to one then a Dremel should work. Use a straight sided burr preferably but ball shape one will also work. Since you have another stock for comparison your good too go. Word of caution - the rear trigger guard screw is in that same area. You may want to remove it while doing this work to be on safe side.
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