Doc White recommends the use of a lube on his PowerStar sabots (not very relevant since you can no longer find them) and claims~..."LUBRICATE THE CHANNELURES IN THE SABOT-IT KEEPS THE BARREL MUCH CLEANER, SLOWS DOWN PLASTIC ACCUMULATION IN THE BARREL AND LOSS OF ACCURACY, AND LOADS EVER SO MUCH EASIER."

Those were a special circumstance but I think if your load is very difficult to seat, a dab of lube wouldn't hurt a thing. Bore Butter used in such fashion would not harm your bore given the cleaning procedure outlined.