I do not own a Spencer...however, I can say that after years of experimentation, I now have no other cleaners or lubes in the gun room, which is dedicated to BP and subs. My son also uses Ballistol extensively on his smokeless weapons, don't see why it wouldn't work on AR's or Spencers. It also seems to work very well, for me at least, as a disinfectant on small cuts, and for anything else that is claimed on the can. Be aware that some folks, especially it seems those of the female persuasion, find the aroma of Ballistol to be objectionable, and are likely to let you know about it.
Count Sandor