View Full Version : Question on 6.8spc AR-15 upper

November 1, 2009, 12:54 PM
I want to get a 6.8 SPC upper for my Colt MT6700 lower. Do I need a complete upper including another bolt carrier or just the upper and a 6.8 bolt.

I am going with a 16" M4 style upper.

November 1, 2009, 01:05 PM
Barrell, Bolt and Mags..... everything else can remain the same.

November 1, 2009, 02:36 PM
The problem with a Colt is that you will need to get a Colt upper receiver so that the holes will match with your present lower. With DPMS, Bushy, etc, you can easily switch uppers with lowers. Colt is different.

You can use the same carrier and just switch the bolt if you must, but I usually spring for a separate carrier. I may be wrong, but I think the carrier and bolt need to break in together and wear together.

Sorry - I stand corrected. I did not realize that Colt had changed their design. My old Colt was from 1990 and had the large pivot hole. I sold it and bought 2 DPMS's with the universal hole.

November 1, 2009, 05:08 PM
no, your colt 6700 shold not be set up with colts infumous larger front take down pin.


heres a pic of my colt 6700 hbar lower with a dpms 6.8 spc upper. it will work out perfectly fine. i would choose a different manufature for the upper though. go with Rock River, as they have a super nice upper and have the correct barrel specs to use hotter ammo with no il effects to you or the gun. happy hunting, brian.

P.S. as to the carrier and bolt, i would go with a dedicated group. its easyier. you can go with changing the bolt head back and forth, but it time cunsuming. nothing will be affected though if you choose to go this way. headspacing is strickly done with the bolt.

November 1, 2009, 07:39 PM
Yup, should be gtg with Colt now, and I'd look at www.titanarmory.net for a complete upper.

November 1, 2009, 08:32 PM
I just ordered a Stag from Legal Transfers complete upper with the most up to date chamber $470.00 2-3 weeks