quote:

Generally speaking, just how far off the rifle lands have you found to be the “sweet spot” for accuracy. And in another question how far off the lands was the bullet when you noticed accuracy begin to deteriorate? I know every rifle is different but surely there must be some parameter bracket in which best accuracy is achieved in the majority of rifles.

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Originally posted by woods:
There are two categories of bullets that have different answers to this question, solid monolithic bullets like Barnes, E-tips and GMX and standard "cup and core" bullets.

In the solid bullets I have always been able to find a suitable seating depth between .030" to .050". I have read posts where the seating depth was slightly more than .050" like up to .070" or so. And then I have reloaded for a Weatherby and used a TTSX that had to be seated .275" off the lands and it shot just fine.

With the standard type of cup and core bullets I have always been able to find a suitable load when seating .020" to .030" off. And then I have reloaded for a RUM that had to be seated .160" off the lands to fit the magazine and it shot a 1/2" group at 200 yds with an Accubond.

There have been several discussions on this around here about the relative importance of powder charge compared to seating depth. For me I work with different powder charges until I find the best group with a standard seating depth (example .050" for Barnes and .025" for Accubonds). An analogy would be a spotting scope with 2 adjustments, a macro for gross adjustment and a micro for fine adjustment. You would not use the fine adjustment knob to do the initial adjustment. Analogously you use the powder charge to get close and then use the seating depth (if needed and often it is not) for fine adjustment. IOW if you had done a good enough job with powder selection and charge weight testing then should not have to move seating depth far (if at all) to time your barrel out.

As far as deterioration of groups due to seating depth, I have noticed problems with velocity variations and thus flyers if I try to seat close to but not into the lands, i.e. less than .020". Any slight variation in seating depth seems to have more impact within that range especially very close like at .005" or so. Over .020" to as deep as you want to seat them, the accuracy seems to go up and down like a sine wave, probably due to minute barrel timing issues. The velocity drops with increased seating depths so essentially you are macro tuning your velocity with the micro tuning function of seating depth rather than using the powder charge variations.

YMMV (especially with rc and HC )

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Originally posted by woods:
Hey rc, your load at 2.30" would be a little skeery for me if just .010" separates it from a bad group. Shooting will lengthen your throat and change the distance to the lands and bullet bearing surfaces can vary substantially even within the same box and definitely from box to box. I record my DTL (Distance To Lands) every so often and those measurements change progressively and sometimes all of a sudden.

I'm not saying that you are going to lose .010" of throat instantly but it is not uncommon for me to record an increase in DTL of .005" from one measurement to the other in as little as 40 or 50 shots. It is quite possible (especially in a 243 WSSM which is known as a barrel burner) that your DTL could change .010" in one box of 50 loads. If they were loaded at the same time and at the same seating depth then you could have accuracy issues. Not saying it's gonna happen just theorizing here.

Do you load small groups at a time like 20 loads or so and then remeasure DTL?

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Originally posted by wasbeeman:
RC, where are your other two shots on each of the targets?

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Originally posted by rcamuglia:
.. Don't you know you're supposed to stop when you have a good group going!