heres a test i did(and had forgotten about until i was looking back through my 260 data)that some of you guys might find interesting.
this was not long after i started fully prepping my brass,neck turing,uniforming primer pockets and de-burring/uniforming flash holes...id just bought a 100pcs of 260 lapua brass and started prepping them when i started thinking this is a lot of extra work...is it worth it?? so i prepped 10pcs and left 10pcs as is outta the box and went out and fire formed the 20 pcs. when got home i FL sized with a redding body die just bumping the shoulders back .001-.002...trimmed to 2.018...neck sized with a lee collet die so while the OD is different the ID is the same which equals about .003 neck tension...cleaned the primer pockets brushed the necks chamffered inside and out primed..loaded and headed back out.
all groups with fired round robin starting with the outta the box...
load was 41g RL-17...CCI 200 primer..139g lapua seated .020 off the lands..this was a very accurate load in this riffle
28" shilen select match barrel
outta the box OD loaded neck .294 to .295
turned neck .293.5
outta the box...............prepped
group 1.......................group 2
2893-2917...................2909-2922
group 3.......................group 4
2896-2930...................2923-2935
so is all the extra work worth it? i guess it depends on what your doing and how serious you are.