You guys are wasting a lot of effort when the press you are using them on probably is out 0.015" or so.
Jerry, this is just silly. You really think that press "alignment" means anything???? I mean, c'mon, you get your press all "aligned" and then you stuff a little cast-iron shellholder into a clip and jam your case into it to rattle around...... The casehead MIGHT be within a few thou before you fire it.....and then, after the case is popped out to straight it's guaranteed to be out of alignment with the case body. In many cases .003-.005 out of alignment.....
Even if you fireform cases, cull them for casehead alignment and re-turn the caseheads until they're aligned with the casebody do you really think that little shellholder clip will promote "alignment?"
Or are you referring to the "alignment" of the threaded hole to the ram?
In ANY CASE, there's no relationship between a "straight press" and the production of straight reloads.
It actually HELPS make straight cases if one loosens up the press with some abrasive paste, free that ram up to align itself....
But all that aside, STRAIGHT dies, dies that are bored and cut with a straight hole and fitted properly to the chamber will produce straight ammunition in any press capable of driving the case in and out consistently.
Conversely there ain't a press in the world that can affect the straightness of the ammo either for good or for bad. No "straight press" will help a crooked die.
For myself, I couldn't care less whether or not the outside of the die is straight but I MUST find the centerline of the hole and adjust for it.
I can't make this adjustment with a collet.
al
Now if someone makes an adjustable collet chuck, a jackable swiveling collet holder mounted to a stout backing plate then I'll switch over to Jerry's method in a heartbeat! I would LOVE to be able to collet to my die body!