Hi guys, been finalizing the details for my first build.  I'm gonna do an RRA lower and Upper, with a 16'' barrel with a 12'' YHM or Larue free float tube.  I want to use flip up sights, so I do not need a barrel with a front sight post.  I see there are numerous types of barrels such as - CAR, M4, Midlength, etc.  Which one would be best for my application?  I also see most barrels are sold with front sight posts on them, so is the norm to just remove them?  Thank you, Joe

You could buy one with the front site base, cut off the top of the site base, and get the midlength LaRue rail.  That always looks sweet.

Dace, when you say midlength Larue rail, what size is that, 9''?  Do you have any pics handy?  I was more set on a 12'' rail.

Not my uppers, but these appear to be both 16 inch barrels.  The barrel on the left has a midlength gas system and a midlength (9 inch) handguard on it.  The barrel on the right has a midlength gas system and a rifle length (12 inch) handguard on it.  As you can see both do not have front site bases.  Only the gas block.



What I am talking about is having a 16 inch barrel with either a carbine gas system or a midlength gas system and having the midlength rail (such as on the left).  But the rifle length rail is nice as well, just adds a lot more weight.  

Ok Dace, thanks for the clarification.  I'm still leaning towards the 12'' rail.  So when purchasing a barrel, do I want a CAR, midlength, or M4.  What are the differences?

Quoted: Ok Dace, thanks for the clarification.  I'm still leaning towards the 12'' rail.  So when purchasing a barrel, do I want a CAR, midlength, or M4.  What are the differences?

Well first you must think of length.

Length: 16 inch, 18 inch, or 20 inch.

Then you get inot profile for each different kind of length.

And you are asking a very big question that would take way to much time to answer right now.  Do some searching and find what works for you.  You should find a barrel you need THEN decide if you need/want a rail.  Build around your barrel.

Thanks guys.  That helps.  I'll continue researching.