Re: 464 SPX Stock
I have no measurements of what I did here, I filed or sanded a little and then reassembled the rifle until I had the desired result. I would suggest anyone attempting this mod do the same.
The angle that you sand or file the end of the adapter to is critical since that is the angle that everything else has to be made to match.
The end of the stock tube, that fits in the adapter, must be filed to allow it to go in the adapter at the new angle. Sand the adapter first and then file the stock tube to fit. You'll also notice the notch in the end of the stock tube, this is to fit around the end of the receiver. The upper side of this notch must be filed, it will become apparent when you fit the pieces back together.
The reason for the threaded rod is because when the angle of the stock tube is changed you can no longer get the Allen wrench into the head of the stock retaining bolt. There is the added problem that the head and washer would no longer sit flat on the boss in the stock tube. The threaded rod works out very well since it firmly holds all of the associated pieces together.
Other than the steel rod, you are just working with plastic so it is fairly easy to do. My son has a 3" wide table mounted belt sander, which greatly helped when sanding the adapter to the correct angle, while keeping the surface flat.
Here is an image that details what I had to change:
Here is completed stock tube, installed (that looks like a split in the stock tube but it's just where it's worn smooth):
The main thing to be aware of is that it's easier to take material off than put it back.