Since I helped my friend work up loads for his gun and went through 4 sets of dies before we found a combo that worked for him I can write this not as an outsider but as one in on the whole thing.. gun build, load development, and bullet selection.
the gun was a custom built Winchester 70 with a Shilen 1:8" target select barrel. the bullets were Berger VLD hunters, the brass was made from Hornady 270 Win and Lapua 270 Win cases. There might be some Nosler cases in there now. I know I am going to be getting some Nosler and Lapua 270 cases for my hunting rounds. I love the 270Win.
we have RCBS, Hornady, Redding, and Lyman die sets. Most after this experiement were sold as they just could not litter the shop. honestly the Redding match/competition seating I think is the best seating die I ever used. the best body die is the Redding 30-06 small base is the best. The best sizing dies I have ever used depend on what you want to do.. neck sizing (Redding S-type), full length is Hornady, and redding standard or gold hunter. What we have now is a Redding Gold hunter sizing die, with a Redding Competition seating die and a Redding 30-06 small base body die (body die is rarely used but it's ready to use any time we need it) We have a full length sizer as the SAAMI min chamber will not allow us to just neck size in some instances.
Berger 135 classic hunter for deer, 156 VLD hunter for Elk.
we found that Winchester ball powders such as Supreme 780 with magnum primers worked to nearly perfection in his gun. powders like Hybrid 100V, H-4831, H4350, IMR 4350 worked exceptionally well. this was with 130 and 135 grain slugs
140 grain slugs were best used with, Hybrid 100V and H4831 SSC.
150 and 156 worked well with, Supreme 780, H4831 SSC, H4350, IMR 4350, Hybrid 100V and maxed out H-1000. keeping the loads at 60,800 to 61,000 PSI was the key for this gun. Magnum primers did much better than standard primers. Trimming the necks to a uniform length made a rather significant difference, and sorting by weight made groupings much better. I like my 270 Winchester too much to rip the barrel off and make it a 6.5-06.
I hope this helps.
Later Suckers..