killerkoala wrote:I have a Tikka T3x 6.5CM LA & am having issues with case & case neck length The books give a SAAMI spec but as a long action can't get enough seat depth into case using Nosler Custom Comp. 140gn Antone have a LA model
I'm guessing you might be trying to seat a bullet long enough to touch the lands?
Action length doesn't change the throat length, but a manufacturer has the option to cut a longer throat in an action that allows longer than standard cartridge length.
Have you actually measured the overall length to the lands already? Easiest is with a flat-ended rod down the muzzle. Rest it against the bolt face and mark the rod at the muzzle with a piece of tape, then put a bullet (not cartridge) in the throat, press it lightly against the lands, place the rod against the tip of the bullet and mark the rod again. Measure between the two marks on the rod for your maximum overall length with that bullet. This is at least as accurate as any other method, to less than .001", and well within the manufacturing variation in bullet lengths.
Personally, I would ignore the lands entirely, but if you can seat the bullet as long as possible, you maximise combustion chamber volume and minimize pressure, achieving higher velocities than if you seat long bullets to standard cartridge length.
Or, is your issue that you can't push a long bullet deep enough into the case to get down to the standard cartridge length because you have too much powder in there?