Need to purchase a barrel for my first build.  What are you guys recommending these days, can I use a 1:9 or 1:7 twist or is 1:8 the only way to go?  There are so many options, AAC, DD, Bravo?!
I bet there are som Labor Day sales going on somewhere.

The type of suppressor has nothing to do with twist rate and twist rate has nothing to do with barrel length. Certain types of ammo perform better with certain twist rates; lighter rounds generally prefer slower twist rates and heavier prefer faster.

Your decision on the barrel should be based on what you plan to do with the firearm (defense, hunting, plinking), are you going to primarily shoot long distance or close range, is your primary concern accuracy, and so on.

The one recommendation I would make is to pick a barrel with a mid-length gas system since it seems to mitigate some of the blow back.

I'd get a 7 twist so I can use anything up to the 70TSX.

Actually when you starry to get really short twist and velocity have a relationship. Get a tighter twist in very short barrels.

Thanks!