The parts for our AR15News 300 Blackout Upper build have pretty much all finally arrived.  I’m getting really excited to get this assembled and shoot it.  So far we’ve shown you the barrel that we’ll be using and also some smaller but important parts.  So that basically leaves us with three final parts to introduce.  They are the Upper Receiver, Rail System and Gas Block.  There will be at least three more posts after this one where we’ll show you what our 300 Blackout Upper looks like once everything is installed, a few accessories that will complete the setup and then a comparison writeup on our range time with the 300 Blackout round.  Check out the pics and specs of the remaining parts below. 

When looking for a new Upper Receiver for our 300 Blackout upper we wanted to take into consideration the composition of the lower receiver as well.  My lower receiver is the MEGA Arms billet GTR-3S which has a darker matte black finish.  Many upper receivers out there will have more of a gloss finish to them.  We will be using the Rainier Arms Gen2 Forged Upper Receiver which matches very well and has a fantastic finish to it.  The Gen2 Upper Receiver comes complete with the Dust Cover and Forward Assist installed and has a small Rainier Arms logo lasered on the top near the charging handle.

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The rail system for the 300 Blackout Upper is the perfect middle ground.  I prefer a longer rail system on my rifles but I also wouldn’t want to completely cover up our awesome Wilson Combat RECON Tactical 16″ 300 Blackout barrel.  We will be using a Samson Manufacturing STAR-MX 10″ freefloat rail.  The STAR-MX is a two-piece design that clamps onto a standard AR-15 barrel nut once the Delta Ring assembly has been removed which helps keep it from rotating.  I really like the look and design of the STAR-MX and am totally impressed with how quick the installation is.  Once its in place it is very easy to align, tighten it up and then you’re rock solid.   It also features two QD attachment points and is designed to be used in conjunction with a low profile gas block.

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I had a spare low profile gas block laying around which is a Midwest Industries Micro Gas Block.  This is definitely a very nice gas block for anyone looking for something similar.  I’ve got one on my 5.56 upper and at 1.125″ tall it fits neatly under my rail system.

Thanks for your interest in our 300 Blackout build.  Be sure to check out the above products at the links listed below. 

The Rainier Arms Gen2 Forged Upper Receiver is available for purchase HERE.

The Samson Manufacturing STAR-MX Rail can be purchased HERE

The Midwest Industries Micro Gas Block is available for purchase HERE.