i am new to the forum, and im sorry to resurrect this, but my newest project is 270 win.
i had a 27" barrel made in 7 twist. the newest 277 military uses 7 twist and a 130-140 gr bullet qt 3k, so that fast of a twist is ok.....
i load 140-175 grain pills. it is a single shot, HOWEVER if a full length bolt action is used a 3.5" col i use might be useful.
my chamber is .600" throated. yes .600". i measure the bearing of each bullet type, and clearance it for .400" freebore which is my number.
caliber and a half for all of my weapons. i also use 24n41 powder. yep fast 50 bmg. even with 175 grain boolits, i have near full water capacity. im not going to publish powder loads, but it gets out a 3k in my chrono at 15 feet. i tried the slower powders reloder22, 4350, 760 and could not get enough powder in them to work. long tapering cases really loaded with 57+ grains and a 175 need slow powder. be careful working up loads.
no accuracy claims yet. im getting there.
i am bill. been loading everything since 1987. lots of wildcatting. i can never get what i need from a box.