One thing for those who have a kit with the left side plate detached from the bottom plate. The first thing you should do is rivet that back together. Having the left and bottom plates as a fixed assembly is critical in the alignment of the RSP. Otherwise you have no constant to go off of.
The only plates I have seen that have holes spotted have them on the inside, in which case it is easy to mock up the receiver and use the bottom plate, etc as a drill guide. The drill will be set on its path by the time it gets to the dimples on the inside. If you have those spot dimples on the outside, that is going to be a bit trickier. What I recommend is to drill the holes undersize and work them to full diameter in a couple of steps. I often mark them with the drill on the assembled box, going just deep enough to be sure of centering the drill the rest of the way. Then I put the flat plate on the drill press and go small. The final operation can often be done with a reamer by hand, with the box assembled. This method often helps you correct minor hole alignment issues with the bottom plate.
Also, I drill to the size of the rivets, which usually finishes at a #14 or #13 drill, a bit smaller than 3/16. This helps keep the rivet straight when hammering or pressing and, done correctly, there will be plenty of material to fill in the slightly larger diameter of the bottom plate holes.
The only plates I have seen that have holes spotted have them on the inside, in which case it is easy to mock up the receiver and use the bottom plate, etc as a drill guide. The drill will be set on its path by the time it gets to the dimples on the inside. If you have those spot dimples on the outside, that is going to be a bit trickier. What I recommend is to drill the holes undersize and work them to full diameter in a couple of steps. I often mark them with the drill on the assembled box, going just deep enough to be sure of centering the drill the rest of the way. Then I put the flat plate on the drill press and go small. The final operation can often be done with a reamer by hand, with the box assembled. This method often helps you correct minor hole alignment issues with the bottom plate.
Also, I drill to the size of the rivets, which usually finishes at a #14 or #13 drill, a bit smaller than 3/16. This helps keep the rivet straight when hammering or pressing and, done correctly, there will be plenty of material to fill in the slightly larger diameter of the bottom plate holes.
