You can use Blackhorn 209 powder in sidelocks equipped with MagSpark 209 conversations.However you must ensure that a very tight overpowder wad is used. A conical/patched ball over the Blackhorn209 powder WILL NOT IGNITE THE POWDER! We have used different loading methods to ignite this powder.
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Blackhorn 209 powder is a clean burning,non moisture attractive,basically non corrosive.