6.8 receiver question

[simplicity]

I've been thinking about building a 6.8 upper for my ar but I just looked through the bushmaster catalog and it looks as if there is a specific  upper and lower for the 6.8, So what this is telling me you have to have a different upper and lower for the 6.8? If someone could fill me in on this I'd greatly appreciate it.

[rockbilly]

The 6.8 upper is available from several sources, and they will fit the standard AR-15/M16 lower.  A couple of other possibilities is the .300 Whisper, or the .300 Fireball.

According to J&T the only ammo recommended through their 6.8 is the Remington Spec. ammo.

I assembled a couple of guns using J&T uppers and lowers, one a 16 inch Expedition Model, the other is a 24 inch match grade.  Both seen to be good shooter, but I haven't fires the match rifle enough to really make a decision on how well it performs, she needs a couple more hundred rounds to get broke in before making final  judgment.

Check J&T out. The "Guns and Weapons," as well as "Shotgun News," just gave Doublestar good marks on fit, finish, and performance.  I am please with the product and price.

     http://jtdistributing.com/store/car_kits.html

[simplicity]

Basically what I wanna do is I have a a2 upper receiver stripped and I was planning on getting a barrel and a bolt carrier and using the upper I already have and the lower I currently use and just switch back and fourth when necessary, then eventually get another lower.
  Like I said before  I saw two different part numbers in the BM cata. and thought I'd ask someone. Thanks for the info.

[teddy12b]

I ordered a regular Bushmaster M-4 lower and then a couple weeks later I ordered the 6.8 A3 Upper.  The the lower is marked as the regular 5.56 / 223.  The 6.8 fits on top and functions perfectly.  I haven't had any problems with mine.  If Bushmaster has two different item numbers it could be because they sell an A2 upper and an A3 upper.  Good luck with your project.