I have been shooting BH 209 in my MK-85 going on 4 years. No misfires, no gas blow-back. I have an original BH 209 booklet that shows the kind of breach plug that should and should not be used. The Knight 209 Breach plug (converted from the original cap plug)indicates that it can be used because the primer is fully enclosed. I will see if I can scan the pictures of the plugs.

There is no mention of the action type, just the breech plug type.

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dogzapper

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