The first thing to try is to apply heat to the barrel using either a heat gun or propane torch. All you need to do is get it just hot enough for a drop of water to sizzle. This will cause the barrel and the nipple hole to expand. Then touch an ice cube to the nipple to cause it to contract while the barrel stays hot. This thermal difference will loosen the nipple and allow it to be removed. However, if it is rusted in place, even this thermal treatment may not be enough to get it to come out. For treating rust, make a 50/50 mixture of acetone and transmission fluid. Acetone is available at any paint store. Put a toothpick or other plug in your nipple and pour the acetone/tranny fluid mixture into the barrel. Let it sit at least overnight and then try to remove the nipple. If you use the acetone/tranny fluid mixture first, be sure to remove all of it before heating your barrel to try the thermal treatment. Both the acetone and tranny fluid are flammable. If you are dealing with rust in your nipple threads, the way to remove the nipple is once you get it to move, don't immediately try to unscrew it completely. Rock it back and forth with your nipple wrench as you back it out. Rust forms in little layers which, when you go to back out the nipple, can layer up and form tiny wedges in the threads which will bind up the nipple again. This is true when unscrewing any rusty threaded thing such as removing a rusty nut from a bolt. Rocking the nipple back and forth tends to break up any rust "wedges" that may be trying to form as you unscrew it.
Oh, BTW, if you use acetone/tranny fluid, be sure to remove your barrel from the stock first. Acetone will ruin the finish on your stock. :cursing:
