Re: How much of the neck to size?
start by backing off 1/4 turn so that the bushing is not on a bind then check runout on a concentricity guage if you have one. this should size about 3/4 of the neck ,that is just fine because with that die you cant size 100% of the neck. .0015 neck tension is good just make sure the neck wall thickness is the same on all your cases so the tension is consistant. and as always if you do exactly the opposite as BartB suggests your going in the right direction.
p.s. have you got a straight 6-250 or is it an improved ??
It takes 43 muscle's to frown and 17 to smile, but only 3 for proper trigger pull.