Ok... this is a complicated question. I actually was thinking about explaining this in detail.
The definition of ammunition is in ch 140 s 121:
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Ok so one should think that powder and bullets are ammunition. Possession of ammunition requires a license or fid in ch 140 s 129C.
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Violating this chapter is a misdemeanor of ch 269 s 10(h):
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But if it's black powder for a rifle or shotgunmade then the prohibition on possess doesn't apply. Right? Look at ch 140 s 129C(p):
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Seems clear enough. Oops don't forget to read those two paragraphs cited:
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So are all BP replicas? If all BP guns are replicas then no FID is required for powder and their bullets. I don't think anyone knows with certainty. But this is why it's assumed that only purchasing requires an fid since that is not exempt. But generally nobody reads further that the BP exemption only applies to replicas and not necessarily all BP guns.