And I want to be sure you aren't trying to stirr up crap.
Have you ever sized a bottlenecked case?
Never mind. I can't work with someone who is so defensive.
Your press is not rigid. It flexes. This flex causes the shoulder of a bottlenecked case to be bumped less than you think you're trying to bump it. The amount of shoulder bump depends on the press, the cartridge, the hardness of the brass, and the amount of expansion of the brass. The harder the brass is to size the less the shoulder will be bumped.
If you raise the ram and screw down the die and jam it against the shell holder the variables mentioned above will cause the die to spring away from the shell holder once the case is inside. This adds anywhere from .002" to .004" to the shoulder length. If you set the die to cam over, you remove the above variables and the die sizes the case to whatever the die and shell holder allow given their fixed dimensions.
In most cases, this bumps the shoulder .008" to .010" from its fired dimension which is excessive. If the goal is to bump .002", we have to back the die off. But we can't back the die off a quarter turn or even an eighth. We have to take into account flex, linkage slack, brass hardness, brass diameter, and the .004" this may induce and only back the die off ever so slightly.
The procedure I described gets you into the appropriate range of shoulder bump right away versus having to back the die off a lot and then going through a lot of trial and error.
The easiest thing to do is to cam over an appropriate Redding competition shell holder. But if you don't want to get a set, then messing with die adjustment is what you'll have to do.
If you use a body die you bump shoulders back to specs and it don't touch the neck and then you can run your brass thru your f/L resizer to get the preferred neck tension that works the best for accuracy
Please take notice that Kevin Thomas shoots for Team Lapua USA and also worked in the Sierra ballistics test laboratory and knows what he is talking about.
I have been reloading for over 47 years and two years ago bought my first Forster full length die. The Forster dies produce the least neck runout of any type of die I have bushing or non-bushing die.
Below the high mounted floating expander enters the case neck when the case neck is still supported and centered by the neck of the die. Meaning the expander can not pull the case neck off center like the lower mounted expanders can.
Below a link at the Whidden custom die website explaining standard and bushing dies, and a very good read. It also states standard non-bushing dies produce the least amount of neck runout.
Whidden Gunworks
Explanation of Bushing and Non-bushing Sizer Dies
http://www.whiddengunworks.com/wp-content/uploads/2015/02/Bushing.NonBushingExplanation.pdf