The thread on the FN SPR action is 1" by 16 pitch. Before measuring headspace be sure the rear of the bolt handle is not contacting the cutout in the action body. I've had maybe 3 or 4 that did so and after correcting they changed headspace by 2-3 thou. Also, maybe 20% of the 15 or so I've barreled had misalignment issues between the action threads and the face. I use a piloted mandrel tap from Dave Kiff that cuts the action threads .010 thou over, and with the tap in the action I dial in the mandrel in the lathe and face the action face a few thou. As to the cone angle, I'm not at home right now (gone for a few months actually) but if I remember right it was around 49 degrees. Easiest way to check that is by placing the angle of the bolt face on the side of your compound and adjust the angle until the bolt body is parallel to the lathe ways. You can cut the tenon to .800 length, and after cutting your cone to the correct clearance and skimming a small face on the tennon face, you'll be right around .750" OAL.