I'm looking to build two match grade uppers (one in 5.56 and one in 6.8) in the very near future.  I haven't fully decided on 18" or 20" for either yet.  But, I'm looking to squeeze as much accuracy out of each.  Any recommendations?  I haven't been following the development of the SAM-R but the 20" barrels seem to the choice right now.

I currently have a 20" Colt heavy barrel in a SPR Mod 0 upper that I've been waiting to rebarrel.  I don't mind the look of a 20" barrel for this setup, but would like to know if I'm loosing anything by dropping to 18".

As for the 6.8mm, I'm totally up in the air.

-Red-

Thanks for the info Wes,

I was just reviewing the 6.8 uppers that you have advertised and noticed that most, if not all, appear to have mid-lenght gas systems.  Is that the standard?  Or is a rifle length system a possiblity for an 18" or 20" bbl?  

Is moving the gas block a waste of time for the longer barrel lenght?

-Red-

Quoted: Thanks for the info Wes, I was just reviewing the 6.8 uppers that you have advertised and noticed that most, if not all, appear to have mid-lenght gas systems.  Is that the standard?  Or is a rifle length system a possiblity for an 18" or 20" bbl?   Is moving the gas block a waste of time for the longer barrel lenght? -Red-

Not Wes. My 16.5" 6.8SPC and its 5.56MM twin (MSTN built), has led me to be a believer in the mid-length for 16" barrels. I have another Recce in progress with Wes, that is mid-length. I believe all the MSTN (6.8SPC) 16.5/18" and LMT MRP 16/18" (5.56MM) are mid-length. The Model 1 uppers, I don't have a clue about, someone else can chime in about them. I will say, that between the two Colt M4 uppers (carbine length) and the MTSN mid-lengths, the mid-lengths win hands down. IMHO..

As far as I know, there is no "rifle length" in 6.8SPC.  My 18" barrel from Wes has something closer to a mid-length gas system.

For 5.56, go rifle when you can (17-20"), then midlength when you can (16"), and finally carbine only for anything that a mid is too long for.

-z