[Azathoth]

Their is a huge discussion on this in the filairsoft forums.

To summarize:

The maker of the EDGI Barrels speculates that it is the Quality of the BB's and ratio between the Diameter of the BB and the inner barrel Diameter that affects groupings.

He measured BB Diameter and found that it varied from 5.89 (excel/KSC) to 5.97 (Goldenball). He found that goldenball BB's fired through stock TM barrels produced groupings comparable to KSC/Excels fired through a 6.03 tightbore. The findings are supporting his theory that their is an ideal bb diameter to inner barrel diameter in the range of 0.11-0.14mm

Originally Posted by Skruface

I also use Big-Out "H"-nubs for my hopup buckings, as they give 2 points of contact on the BB as opposed to 1 with a standard hopup bucking.

I use the SCS, I noticed a huge groupings improvement over standard nubs and "H" nub that is in line with what is seen in filairsoft. The other noticable difference is the amount of hopup you can put onto the BB.