Originally Posted by redgun
I am using a RCBS Rockchuncker press w/ Redding comp seating micrometer dies (7 WSM and 6BR, loading Berger VLD's in both) and getting bad runout on the loaded ammo. I have already added VLD seater stems to both dies.
Brass on both has been neck turned and being resized with Redding neck bushing dies.
Any suggestions as to what part of my equipment could be to blame/need replacing??
well you've stated that you have the same issue with two different die sets, so the next thing to check is what a resized case looks like. They'll also show a similar issue; my guess that is. If so, the next thing to look at is the press (here we go again). My suggestion is to find somebody with a different press, and try the same setup on their press. I simply cannot imagine you having two bad die sets in a row, although Redding did build quite a few bad 6BR dies sets a few years back. If they are bad, then good luck talking with them because 98% have zero luck with them.
I shoot for a .0025" TIR window when loading ammunition (+/- .00125"). I don't always get that number but usually come very close if I don't. If your problem comes with just the seater and not the case body's runout, then you might have a bad seater. My guess is that the sizing dies are where the runout starts, and a seater can never correct this issue. If it is in the case, start with the shell holder(s). Look closely at the surface they set on for a burr or even something that will cause the shell holder to not seat solidly in the ram (I've seen this one many times). Now take a case that you know is good, and seat in the holder, but leave the retaining mechanism slightly loose. Install the sizer die with the jam nut slightly loose, and size the case. When the case is all the way in the die tighten everything up. See if the case is good. If not, it's time to try another press.
Presses with a single spindle type rams will torque a little bit during their upwards travel. (they have no guide rods to maintain alignment.) If your still seeing runout now, pull the link bars from the ram. See how much movement you have between the bore of the press and the ram. If you see .002", you can pretty much double that for minimum runout (TIR). This issue is quite common. If the bore is bad, the fix is a pain in the butt.