The Samson front sight came in. The length of threaded part of the post, and the height of the post itself, are basically equal on both the Troy AND the Samson front posts,
so they ARE interchangeable. So far, so good.
But not so fast...
To get the Samson front to work with the Troy rear like some people have done, you must ask Samson to send a shorter post. That shorter post not only has the threaded part of the post shortened by half, but the upper part (the post itself) is shortened as well (by about one-third). This all means that I'll need to shorten my Troy tritium post to make my idea work. The deal breaker is this...the Troy tritium front post itself, is made up of 3 pieces, and the threaded part cannot be cut short or it will basically fall apart. Yeah...that tiny front post is made up of three different pieces. Shortening the post is really the only way to make any Troy/Samson configuration work and get the sight to zero.
Here's why you can't shorten the Troy tritium post like you can the Samson post:
The Troy tritium post has 3 pieces: 1) a lower threaded sleeve; 2) an upper post that slides down into the sleeve; 3) a SS retainer ring that keeps the two together. Shortening the lower threaded sleeve will cut off the retainer ring, causing the two pieces to separate. The upper post is more of a blade rather than a square post. It's made to rotate within the threaded lower part so that you can make quarter-turns up or down for elevation, then re-orient the tritium vial separately, so that it is again facing the operator. The retainer ring must stay intact. See photo link for further explanation.
http://www.metalworld-photo.com/TroyTritiumPost2.htm
In the end, I decided that I'm going to sell the Samson post, buy a Troy BattleRail, and just mount both Troy sights on this one piece rail. Since mine is a P556 pistol, I think that any play that could be in the front of the rail, if there is any, would be acceptable considering they are back-up irons, and it's a pistol. The chances that I'd really need to hit something at more than point blank range with the back-ups (after my EOTech fails) is very remote.