I wanted to get some opinions on my 3 gun rifle build.  I am new to the sport but wanted to put together a rifle that I wouldn't have to modify much down the road rather than buy a gun and change everything.  So here it is:
Aero precision upper and lower receiver
Noveske 18" stainless SPR barrel with headspaced bolt
Surefire compensator
Geissle trigger 3gun
Samson handguard
JP Lo mass bolt carrier
JP buffer system
ACE socom buttstock
Vortex 1x4x24 optic

I think that covers it.  Let me know what you think

On the east cost we typically have shorter ranges on the rifle shots.  I am shooting a 12.5" Compass Lake SBR for example, even though I have a 18" MK12.  If your not taking 500+ yard shots you may want a shorter barrel.

I can't stand the Geissle 3-gun triggers.  AR-Gold on the high side, or Timney or CMC 3.5 that are cheaper are all a lot better than the G 3-gun trigger, they have shorter resets and you know where the break is at.

The Low mass parts only if you are going the adjustable gas system route, and there is not a big advantage either way.

Red Dots are faster for close shots, The Burris 1-4 is easy to find and hold overs are suitable for 3 gun.  The SWFA is more like the Vortex and appears to be a better overall scope to me.  I am personally shooting the Burris still, but have several of the SWFA 1-4x, and sold my Vortexs.

HAHA so basically you hate my set up..  I have a geissle in my Tavor and love it.  the courses near me will be shooting out to 400 so a longer barrel sounds like the best bet for me.  Low mass parts can be used as long as you have the correct buffer spring in the gun.  You do NOT have to have adjustable gas to use them from what I understand

Yes you can use the low mass components without adjusting the gas system and it will function, however the recoil will be more than if you had used standard components.  The low mass BCG allows you to turn down the gas a lot (with an adjustable gas block or key) and still cycle, giving you a softer shooting setup.  

I'm not sure what the Tavor Geisele is similar to in the AR line, but I've had 3 of their 3gun triggers and the pretravel and reset are longer than the other triggers I have tried and there is no noticable break point so it hurt me on precision shots.