All Sum barrels are all Broach cut, but production reamed (on the tight side).
The downfall to Broach cut barrels is when the do give up the ghost, they fall of the mark very fast.
Trust me, unlike a button produced barrel which may be still usable for another 1000 round of match shooting since the groups open up slowly over that many rounds, around the 2500 mark, The broach cut barrel's is going to go south in like one of two shooting.
Rule of thumb is that a broach cut barrel is good for around 2.5K rounds (in the groove), and a Button produced barrel another 1K over than mark due to still semi staying in the grove as it wears out. As for hands down the best shooting when still in spec, the broach cut due to sharper lands/grooves, and no barrel tension caused when producing the rifling.
SCvARminter, so you don't think we forgot about you,
Keep in mind that the Sum barrel is tighter chambered in 223. Surplus 5.56 ammo and the Sum barrel are a bad combo since you get way high working pressure and often lead to case sticking in the chamber. Also, depending on what the end product of the rig is going to be, compass lake does offer custom Douglas barrels that will hold there own with the Sum barrel (read even better due to lapping and custom chambers so they are taylored to the ammo and don't need to be broken in). If you don"t want to take a chance of getting a production produced barrel that won't print, then you may want to spend a couple extra dollars and give Frank a call and talk to him about barrels.
www.compasslake.com/P.S. welcome to the site!!!!!!