Hossman, for your reading pleasure, I just now went through my process again to determine OAL for the ACME 124gr RN-NLG and my CZ-75 ShadowLine. I loaded a dummy round (resize case, flare, seat, crimp), then seated .005 deeper, deeper, deeper, until it would plunk and spin freely. It was
NOT spinning freely at 1.079. It
WAS spinning freely at 1.074. To determine a working OAL, the recommended reduction from the maximum is .015. I typically do a reduction of .010. In the past, I have loaded this bullet to 1.060 or 1.065, so it appears my OAL determining process today lines up nicely with the first time I loaded this bullet however long ago.
You, however, were loading this bullet to 1.078. My ShadowLine is a little more short-throated than most, so it's not uncommon for people to load the same bullet a touch longer than what I load, so a little variation doesn't surprise me. However, it's your results that matter, and your results are telling you that 1.078 is too long. It's THAT simple.
I don't know that your arbitrarily knocking off .008 to get it down to 1.070 is the right decision here. YOUR original process was in one way or another wrong. My recommendation is that you do it again. Determine your maximum OAL by one of the methods available, THEN knock off .015. Let THAT be your working OAL. If that turns out to be 1.070, great. If not, also great. I would just redo the whole process so that you have a more complete vision of what's going on.
