A friend of mine had been complaining that he was getting a lot of run out on his bullet seating a few weeks back. When I ran into him last week he told me he had found a cure for the issue. Turned out the spring that holds the shellholder in to the ram on his RC had been tilting the shell holder a bit. Removing it and cleaning the groove where the shellholder fit almost eliminated the runout entirely. I just tried in and while on my bolt gun cases I always get good numbers, I just checked 25 loaded .308 rounds and had runouts of .002 max on 5 rounds, .001 on 8 rounds, and less than .001 on the remaining 12. Bit of a pain because you really have to take your time inserting and removing cases but if you have a runout problem it is worth a try. It costs nothing and you can always put the spring back if it does not work for you
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Someone shared a quick tip on concentricity
- Thread starter hounddawg
- Start date
That's interesting. It is possible to design a spring retainer not to tilt the holder. I'd have to look at a Rock Chucker (I don't have one) up close to get some idea what is going on there. But if the tilt is intrinsic in the design, you might mention this result to RCBS so they can consider making a change.
One thing I like about the Forster Co-ax press is the case head sits on a flat surface while the automatic shell holder jaws just retain it. That way, there is only an issue if your gun is fireforming case heads out-of-square with the case body (in which case, it is usually time for some work on the gun).
One thing I like about the Forster Co-ax press is the case head sits on a flat surface while the automatic shell holder jaws just retain it. That way, there is only an issue if your gun is fireforming case heads out-of-square with the case body (in which case, it is usually time for some work on the gun).
This has been a known issue with some RCBS presses for many years. My original JR press would give visible runout (rolling cartridges on a glass plate, didn’t have a runout gauge then), but grinding the end of the spring down so that it just barely retained the shell holder almost eliminated it. This was back in the late 1970s, I read about the hack in a Gun Digest if I recall correctly. Obviously the top of the ram and the shell holder must be kept clean regardless.
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Yes... back in the seventies it was common for RCBS press owners to remove the spring, bend it so that it gave less pressure on shell holder (just barely keeping it in the ram).This has been a known issue with some RCBS presses for many years. My original JR press would give visible runout (rolling cartridges on a glass plate, didn’t have a runout gauge then), but grinding the end of the spring down so that it just barely retained the shell holder almost eliminated it. This was back in the late 1970s, I read about the hack in a Gun Digest if I recall correctly. Obviously the top of the ram and the shell holder must be kept clean regardless.
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