Been using the plain old bore butter on the breech plug threads for 3 seasons now with the inline and not a problem. I also use a 1/2" copper fitting brush, you know the kind the plumbers use to clean the inside of sweat fittings to clean out the threads on the breech itself as the bore butter will gum up in these and cause problems. You only need to put a tiny bit of BB on the leading threads (I put 3 evenly spaced dots on to ensure coating)of the plug, to much and it will ooze out toward the rear once installed. If you can see a fine yellow bead at the back of the breech plug you did it right.