No drilling needed.
As you look at the receiver from the side, the bolt catch is wider than the slot in the receiver. Material will need to be removed from each side of the bolt catch. This is the Gen 2 part, there is only one part number. It is also clearly not the same quality part as the Gen 1.
If you have access to a good stone, you will be fine removing a small amount from the bolt stop to get it to fit with out any problems to the bolt stop.
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