You can get them fairly inexpensive one on EBay just do a word search for “AR10 upper receiver block”. If you don’t plan on removing and installing a bunch of barrels. If you want the best way to go about it, go with a “Reaction rod” the rod engages the barrel extension and is bullet proof when it comes to serious torque and it does not stress the receiver at all.
I've looked at the reaction rods and they appear to be a better, or safer, way to go and as is par for the course, they're also the most expensive too.
Appreciate the help!
