Does anyone know how far forward the fins carry inside the rail? While installing the gas block after the rail is slid on sucks, alignment shouldn’t be a problem if the block or shaved FSB is installed using taper pins. If the fins stop at the 7" gas port location, there’d be room to manipulate the rail for a midlength gas setup to get to the pins through the keymod holes. Not ideal or as clean as a NSR or CMR install, but a workable solution.
I installed the 15" version on a 16" carbine today. I threw the parts on the scale before I installed them- 15" rail, barrel nut, the 7 mounting screws, and the shim package came to 11.5 ounces. They quote 9 ounces for this rail, so I’d guess that you could add 2.5 ounces to each rail weight for barrel nut and screws.
I used a set screw gas block, and dimpled the barrel. I sighted down from the end of the rail to insure that the gas block wasn’t cocked, and adjusted it by tapping it with a punch through the keymod holes. The screws lined up perfectly with keymod holes, which made it easy to torque the screws down, and staking the screws wouldn’t be hard either. The fins end about an 1/8" short of my gas block, if you installed this rail on a midlength, you could probably slide the rail enough forward that it would slip off the barrel nut, which would allow for a lot of free movement to make tightening screws, or even setting pins fairly easy. The fins only extend up to the gas block, so they wouldn’t get in the way of a suppressor.
overall I’m pretty happy, even if it’s a bit of a pain to work on.
+2…fsb carbine cutout…slender and round…I won’t be purchasing any rail till these specs are met.