My 6400 was staked in a couple of places. Look at the slotted castle nut. A steel punch on the edges of the slots and a hammer, got it past the staking. It will mar the finish on the slotted nut, but I had no intention of reusing the fixed telestock. There are wrenches available, but I didn't have one at the time. For reinstalling a new tube/receiver extension, it is recommended to use a little bit of blue loctite on the threads instead of staking. This is to prevent loosening. Loctite is available at any auto parts store or similar. If you are looking for something to help loosen the tight nut, use any good penetrating oil, but that will not help if the nut has been staked. Good luck.