The other day I bought a Sig M-400 stripped lower receiver and a stripped upper.  I was wondering what to make it into; 6.5 Grendel but I bought a Bear Creek Armory 6.5 Grendel side charging Upper with a 20" stainless heavy barrel; 1:8 twist.  

So here I am still with a lower/upper, what to do?  It came to me - I have a .300 Blackout pistol barrel from when I tried to convert my Olympics Arms OA-93 pistol from .223 to .300 BO.  So that's the direction I'm going to go in.

Here's what I think I need; please add to the list if you notice something I haven't got on the list:

Lower (already have the lower parts kit installed)
Upper Parts Kit
Forward Assist
.300 BO Pistol Barrel - have it
Bolt/BCG
Gas Block
Gas Tube
Pistol Hand Guard
Front and rear sights
Buffer Tube
Buffer Spring
Buffer
Folding Arm Rest

Thanks

flash hider of some kind

skip the irons and just get a halfway decent red dot

Get an etched reticle prism sight. Not battery/electronics dependent.

I have two of the Vortex Spitfires and I like them a lot.