Beads and posts are legal. A bead in this context is a post. The spirit of the rule is no aperture type insert where you circle the target. Either in the shape of a "donut", or specific "Target animal" eg. chicken insert for a chicken. Let's not overthink this rule.
With all due respect you are wrong about that. The entire rule reads this way...
Page 8 from the March 2005 Rules read
" *3.1.3 Cowboy Lever Action Silhouette Rifle
1. Rear sights may be open sights, receiver or tang sights manfactured for the rifle they are mounted on. Front sights must be a post or bead, may be hooded or if interchangable may use the post inserts only"
A bead is NOT a post, if it was in the sprit of this rule, they would have seen no reason to say "must be a post OR bead".
Right, wrong or otherwise, the current rules do not allow you to use a bead if the front sights are interchangable.
Thanks,
Chicken