Building an AR upper in 6.8spc

Kenthetoolman

January 22, 2012 09:33

I am thinking about trying to build my first upper and would like to do one in 6.8spc. As I understand it, I should be able to put this on my Rock River 5.56 lower without any modification. Is that true?

0

• 

  Mobuck

  January 22, 2012 11:26

  That is correct BUT I have a few reservations.
  If you don't already know the answer to this basic question, are you qualified to "build" an upper?
  I don't mean to jump you but the upper is the part that actually contains the pressure and sends the bullet on it's way. Assembling an upper requires more tooling and mechanical knowledge than driving some pins into a lower.
  Good luck and be careful.

  0
• 

  62fuelie

  January 22, 2012 13:01

  When I decided I "needed" a 6.8 AR I bought an assembled upper and built the lower. I used a 5.56 spec lower and it works just fine. I second Mobuck's concern that you get the headspace and other critical dimensions correct for your own safety.

  0
• 

  armilite

  January 22, 2012 15:27

  There is nothing one can do with an AR to adjust head spacing. You slap the barrel on the upper and torque to 50lbs. or so. Put in a new bolt and then try a go, no go gauge. If it fits your good to go. If it doesn't you need to try a different bolt. There is nothing else you can do. There's no thing as shims or spacers, if you buy quality parts you'll have a 99.99% chance of a properly head spaced upper.

  0
• 

  v35

  January 22, 2012 20:13

  Get the barrel with a barrel nut installed.It then will be headspaced.
  The rest of the assembly goes easy with an armorers tool and action block.
  Assembly is a better term.

  0
• 

  Mobuck

  January 23, 2012 02:15

  Incorrect Mr. armilite,
  If you start with a bare barrel, the chamber is reamed to set correct headspace when the extension is installed. Granted, most barrels come with the extension installed, but one cannot make the universal statement that"nothing can be done to adjust headspace".
  We who have some knowledge of the AR must be careful not to mislead others who know less.
  I get particularly cranky when a discussion starts with "I want to build xxxxx" since there is a quantum leap between assembling lego parts and building a firearm.

  0
• 

  armilite

  January 23, 2012 17:05

  quote:Originally posted by Mobuck
  Incorrect Mr. armilite,
  If you start with a bare barrel, the chamber is reamed to set correct headspace when the extension is installed. Granted, most barrels come with the extension installed, but one cannot make the universal statement that"nothing can be done to adjust headspace".
  We who have some knowledge of the AR must be careful not to mislead others who know less.
  I get particularly cranky when a discussion starts with "I want to build xxxxx" since there is a quantum leap between assembling lego parts and building a firearm.
  
  
  
  Seriously how many people buy a barrel without the barrel extension. Really if you asked anyone of these new to the AR world and even some that aren't they'd have no clue as to what a barrel extension even is. Anyone buying a stripped barrel would know this and I'd be willing to bet 99.9% of the members here did not buy a stripped barrel when they assembled their rifles.
  I don't think for a minute that anyone that comes here to ask about building or assembling a rifle for themselves is starting with a stripped barrel.
  So for the record I'm stating that there is nothing you can do to adjust for head space on a complete barrel including the extension other then to try a different bolt.

  0

Please sign in to leave a comment.