Buffer spring/buffer for 6.8spc

AR/M4 Beyond 5.56/.223
1

Is there anything special I need to be concerned about for the 12.5" 6.8SPC SBR i am building? Is there a special buffer/spring for it, or does the standard H buffer and spring for the 5.56mm work without issue?

Perhaps I should give more info:

The upper will be a 12.5" barrel with a mid-length gas system, a noveske or paladin switchblock (I havent decided which one I like better), with a phantom or bird cage supressor (have both), and may eventually have a sound suppressor installed. The bolt carrier group will be BCM.

Thanks in advance.

2

It depends on the ammo and gas port size. I tend to pick H2 buffers and then set the gas port to it.

3

Why mid on a 12.5"???

4

I am not a gunsmith, so I am going on what I was told. My understanding is that the mid-length gas system on the 12.5" 6.8SPC upper helps with reliability if you use ammo from either end of the spectrum (Remington or SSA Tactical).

If this is untrue, I would love to know what is the most appropriate length. I have mids on my 5.56 rifles, but they are both 16" rifles and not 6.8SPC.

5

What are the dimensions of a carbine gas system versus a mid-length gas system?

6

One of the guys I have some acquaintance with wrote this up:

http://www.03designgroup.com/technotes/carbine-vs-mid-length-gas-system

Now this is for a 16" rifle. Also, he just details what they are, and what he has observed, and what is fact, not all of the technical details about each length…