trophy hunter

Using BB as a breech plug grease may be a little risky, but if it works for you????

One thing that may allow it to work for you is the quality of the rifle you have and the mating of the breech plug face to the flange in the barrel. If this seals and no-blowback goes beyond that seal - back into the threads you SHOULD be alright, but, if you start getting blow back into those threads - you might be in for troubles....