ocw test method

[mikecr]

I first performed a seating depth test using a starting load and found -0.060 to be good. At this depth, all 3 shots were touching. Above or below shots were 1" groups or larger. (I use the Berger test with 0.040" jumps, then test around a good group in smaller steps if necessary) I then did my load development using this seating depth and found a good node. I then did another seating depth test (to me this is "tweaking seating depth") and found that my best depth now was -0.030. I then loaded up rounds at my new load and at +/- 0.2 gr using the new seating depth to test that they would all shoot in the same group. They all shot in a sub 0.5" group. Dennis

I like your post Dennis. Good information.
I've seen similar and larger dispersion with seating testing, which is my basis for declaring it as 'coarse'. I've never seen powder adjustments cause so much dispersion, so to me powder seems more 'fine'.

It should seem to many that load development truly is unpredictable. Among many things, there is also a matter of our individual goals.
My goal to begin is pure precision, even if managing several attributes on a razor edge to get it.
I'm confident that your 30thou 'tweaking' of seating, at best powder, changed more than a seating result in itself, and in violation of Berger's testing method you had correctly completed earlier.
I think that 60thou is still better, and that your powder is not best at that.
So I would have stayed at .060 OTL and sought a powder load that shot best there, then tweaked seating no more than ~10thou for group shaping.. Where your results returned sub 0.5" and forgiving at that, my results might have been sub 0.3" and less forgiving. Again, there is no hard predicting of it.

 

[T-shooter]

This is a seating test I did several years go, shot round robin style. It did seem to like one specific seating depth.