If it's a neck sizing die then you want it screwed down just far enough so the shellholder just barely touches the die when the ram cams over. Same is true when you are useing a full length sizing die and you want to FL resize the cases. Sound like you didn't adjust the sizing die right and are having headspacing problems because if it. On rimless rifle cartridges the datum point for headspacing is right where the neck and shoulder meet. If this isn't bumped back enough (not usually a problem when just necksizing), or if the base of the neck is oversized, the cartridge won't fit right. If the COL is correct based on the bullet you're using (don't just look at MAX COL. Max COL just tells you how long the cartridge can be and still fit and function correctly in a magazine-fed weapon (many BR shooters intentionally seat the very long and heavy VLD bullets well past Max COL because they shoot single shot rifles or just don't use the magazine). But reloading manuals will also have a published COL for each bullet or family of bullets based on the shape of the shape of the bullet, and this is the COL you need to go by if it is shorter than the Max COL. If not COL is listed for the specific bullet you're using, or it's listed at the MAX COL for the cartridge, then you should be good to go unless your rifle had a unusually short throat (which is not generally the case with factory chambers, in fact, the opposite is usually true). Re-check the COL against the manual, and once you're sure that's ok, then the next step is to resize them correctly. I'd do a FL resize just to be sure.

Word of warning: If you choose to pull the bullets and resize, REMOVE the decapper on your die. DO NOT attempt to deprime live primers!!! Primers are very powerful despite their size and if one detonated in your die could cause serious injury or death.

Good luck and let us know how it works out.

Mike