Bullet Runout

[WildWest]

Newby here.

I just purchased an RCBS Case Master to check bullet runout. It appears that 60% of my finished product is coming out at between .005 and .010 runout. My resized,shot once) brass is mostly about .001-.002 out.

I am loading for a .300 WSM to be used for hunting. The bullets are 165 grain, Barnes TSX. I have Hornady dies.

The questions I have are:

1. How much runout is too much? Is 0 runout possible?

2. Where on the bullet should I measure? Close to the point or at the area where the rifling will contact the bullet?

Thanks in advance for any comments.

Stu

 

[Winchester69]

How straight is your brass after sizing? Under 0.002" is very good. If your sized brass isn't straight, you need to look at the sizing process. Slop in the ram/bore of your press will cause misalignment. The best way to find the problem otherwise is to check out your pieces one at a time. Use your dies on a friend's press. Use his dies on your press. Compare the run-outs.

If your brass is straight but your bullets are loaded crookedly, experiment with your seating technique. Rotate the cartridge once or twice during the seating process. Using a sleeved seating die can be a good investment,Redding Competition or Forster, micrometer optional). Check how the seating plug fits the bullet. It should not contact the tip of the bullet.

Zero, if possible, is unmeasurable. But you can get close. Under 0.001" is excellent, but won't mean much in your rifle's chamber.

The farther out on the bullet the run-out is measured, the more it will be accentuated, but may include other errors. Closer in is easier and is probably a better indicator of the misalignment error.

 

[britz]

I'm a hunter and a little new to the runout stuff, but I try to keep it under .003. I consider anything over .05 very bad and cull those out of my lot. Obviously I'd like to see it all under .001.
I have also found that much of the runout is caused by the cases - expander ball comming through the case in particular. If you can, get rid of the ball. If yo cann't then just polish it up really good with very fine sand paper or emery cloth. THis should help.

 

[WildWest]

Thanks Win69,
I think I may have found the problem--My shellholder/ram fit is poor. I have an old Bair press and a new Hornady shellholder. It looks like the shellholder can't go into the slot far enough to be flush with the ram. I'll try your suggestion and test my dies in another press.

So, how much is too much for bullet runout? I guess I'm asking when do you pull the bullet and start over?

Thanks again.

 

[Winchester69]

So, how much is too much for bullet runout? I guess I'm asking when do you pull the bullet and start over?

I'll refer you to a comment I recall John Barsness making in an article he wrote a number of years back: for hunting, 0.004" run-out is a good max. Of course, the bottom line is where they're landing on paper. You have to write your own standard.

I reread your post after answering and noticed that you are only getting 0.002" run-out on sized brass,I was reading fired and unsized). I chose to leave my commentary as was. The problem you have described with your shell holder should affect all press operations; I don't have a clear idea of where the problem arises. If your brass is straight and the bullet is crooked, I would concentrate on the seating process. Using a VLD chamfering tool will assist the bullet's initial alignment. Once it starts crooked, there is no tendency for it to straighten itself. Check how the seating plug fits the bullet tip. The plug can be modified to improve the fit. I mentioned rotating the cartridge. It is a popular method, but one that to me implies an uneven distribution or alignment of the ram force. I'm a little skeptical, but maybe everyone else isn't wrong.

Recognize that your run-out gauge has only identified a process problem. Once the problem is resolved and your process has found its capability, it won't improve itself further. Don't make run-out a holy grail. If your bullets land where they are supposed to, your run-out is satisfactory. Further improvements will only be recognized through changes,improvements) to the process.

I will add one further line of commentary. If your shell holder is cocked in the ram, it may be that the force required by the sizing process aligns the shell holder, whereas the seating force is sufficiently less that alignment is not achieved. Just a thought.

There are those who advocate replacing the metal retaining clip for the shell holder with a rubber O-ring to allow the shell holder to align itself. If the retainer is a problem, this could be an area to experiment in.