My new RRA stripped lower receiver is baking under a fresh coat of Moly Resin and I'm looking into the rest of the parts I'll need to complete my build.  I have a few questions for the hive.  First, an idea of what I'm after:

16" barrel, midlength gas system, 1x7 twist, chrome lined, Vortex on the business end
Low profile gas block
Midwest industries MCTAR-22 FF rail system to go over and forward of the gas block

Has anyone built something similair to this?  I'm expecting someone has.  A few questions...

-Which low pro gas block should I use under the M.I. FF tube?
-Which manufacturers make this particular barrel?
-Do the low pro gas blocks use the pins that need to go through the lower portion of the barrel?

I have one RRA and I've been very pleased with it thus far so I intend to use RRA parts as much as possible.  RRA doesn't offer a midlength barrel without the FSB so I figure I'll have to go to another manufacturer for this.  I plan to use a magpul stock and grip, A.R.M.S. #40L B.U.I.S. and a rail mount front sight.

-Do any of the manufacturers make a rail mount front sight with the round hood (H&K style)?  

Thanks for taking the time to read.  Any advice would be greatly appreciated as I'm not the most patient person and doing the trial and error thing would drive me out of my mind.

Anybody?????

Quoted: Do the low pro gas blocks use the pins that need to go through the lower portion of the barrel?

This is the only one I can help you with, as I haven't used any of the specific products you've mentioned above.

Gas blocks will use set screws, as there is no way to line up the holes in the gas block with the existing holes (notches) in the barrel. The holes drilled in the edge of the barrel have no set spec where they are drilled -- the spacing between the two holes and their height will be different even between barrels from the same manufacturer.

Thanks for the info M4M!