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OK, so I've taken everyones advice on my Concentricity thread and removed the expander balls in my dies. I loaded some up and sure enough the concentricity improved.
But what about presses? Does anyone pay attention to how square their reloading press is? I know that arbor presses and special dies are 'better', but what about the old standby single stage press?
I recently bought an RCBS AmmoMaster 2 (large enough to handle the 338AM I have ordered). For those that aren't familiar with the press, there are 3 columns that hold the top of the press above the bottom of the press. It's not all cast as one unit like the RockChucker.
I got to thinking 'what if those columns aren't exactly the same length? Or what if the holes that are drilled in the top weren't drilled EXACTLY the same depth? If either of those things happened, then the top would not be parallel to the bottom and would not be square to the ram. HMMMM??
So, I just spent the last hour measuring its 'squareness' from the bushing on top of the press to the top of the ram.
After countless measurements at full stroke, I've determined that the front of the hole is .005"-.007" further from the front of the ram than the back of the hole is from the back of the ram. The side to side is very close (probably around .001" if not closer). This would mean that the dies would actually slightly tilt backward.
By carefully dressing the front support, I believe I can make the top square to the ram, but won't do it until I figure out the absolute best way to repeatably measure the differences.
I've done some searches looking for a discussion about squaring a press etc. if it exists, I can't find it.
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You could shim it on the bottom or top until it is dead nuts on. But until you measure it under a full compressive loading, you won't actually know for sure how out of square it is.
A quick test would be to screw in a die and then bring the ram to full contact. With pressure on the ram, use feeler gauges to see if there are any gaps between the ram (shellholder) and the die.
FWIW, The case should still go into the die squarely since there is enough clearnace in the shellholder to account for the apparant lack of squareness. Hope this helps.