I shoot the Carbon Express terminator hunters and really like them. Have been using carbons for 3 years now and don't see a change coming soon, "but" I was checking straitness on some used arrows a friend gave me for my son to shoot, all aluminum xx75's and gamegetters, and the good ones were all really good. .001-.0005" for the xx75's and I thought I would compare to my new carbons to see what I could get away with for him to use and the carbons were all .003-.006".
Now these are the same kind and checked out at the same spec as my used practice arrows and I am taking these and checking fixed blade heads and hitting 2-3" groups at 30 yards with them. I hear some people bashing carbons because they aren't very straight but I really don't see a problem with that 'cause of the broadhead groups I am able to get with them.
So if you are getting better groups with them it may be because they are spined better for your setup than your old aluminums, or maybe your old arrows were slightly bent, or maybe it is just the confidence that having new arrows gives you.
Whatever the reason is.......
It's all good!!!