I have been using a RCBS partner press to load ammo for some time now (I also use Wilson style hand dies that produce straight ammo). I am having a problem with rounds that have a lot of runout (usually MORE THAN .005), and I have tried every trick I know to make them better. Could the press itself be the problem? I ask because I have dies by RCBS, Redding, and Lee and there are none that produce straight ammo. Some brands/calibers are worse than others. Has anyone else had experience in this area. I think rounds with excessive runout are limiting my accuracy. I read about by a benchrester that stated that more than .005 runout can have an effect on grouping as large as 1/2" at 100 yds. Any help would be appreciated!!!

Do you have a press you can borrow from someone to try? I really cannot imagine how this could produce crooked ammo though. If the ram were offset it would show up as an offset base not neck. Have you turned the necks at all? What calibers are you shooting, more than one? How about brass, have you tried using different lots? Did this just start happening? How are you measuring the runout?

Sorry for the questions but when you have a problem it helps to have as much info as you can.

The majority of runout problems are usually in the neck as a result of the expander in a conventional die. This can be worse if you have a press that has runout in the ram, which most of them do. That is the reason the instructions for setting up the dies generally suggest the shellholder butt up against the base of the die so that the ram "cams over". If the die is secured at that point the runout created by the press is minimized or eliminated. That's the area in which you are likely introducing runout. It follows that the seating die can do the same. Die adjustment has a huge bearing on how concentric your loads will be. You'd have to be a bit more specific on your loading setup for any more specific help.

Hey Don, I'd suspect the Runout is caused by Neck Sizing when the Case is not fully supported within the Die. Lots of folks experience the same thing as you and go to inordinate amounts of effort to resolve the issue.

On the other hand, I prefer to Partial-Full Length Resize(P-FLR). This forces the CenterLine of the Case to become closely aligned with the Chamber's CenterLine as the Case is held in Compression between the Bolt Face and the Datum Line of the Chamber Shoulder. Due to this, I've never worried about Neck Runout, and don't bother measuring it.

It is easy for anyone to run a "Blind Test" to see for themselves which method it best. Just load up 12-18 cartridges that you P-FLR and a similar bunch that have been Neck Sized. Have a buddy give you the cartridges so you don't know which ones you are shooting. If you know for sure you "Pulled a Shot", go mark it, and do not include it in your final assessment.

Every few years I re-run this Test myself. Last time I did it was with a very accurate 223Rem. Just as always, the P-FLR cases shot "slightly better". Not much, but enough to know for sure there is a difference "for me".

Best of luck to you.