If I want to basically cover up most of a 16 in. barrel with a Larue rail, which will work best? The 13.2 or the 12? Also will it work with a milled off Bushy FSB or need a lower pro gas block instead? Thanks.

O.K. I thought the question made less sense this morning. Anyway, I got a pretty good deal on a new larue rail. I only have 16 in barrels, so which rail would you use if you could pick any of them for the same price? Thanks again.

Well, obviously, if you want to cover more of your barrel, you should get the longer rail.  It requires a low-pro gas block too.