Seating runout

[petenz]

I got a sinclair concentricity gauge recently, and have been having a good play with it. It's confirmed what I had suspected - that I am somehow getting a lot of runout in my seating process.


My .243 cases, sized in a lee collet neck die, have about .0015" of runout, max.


However a loaded round can have anything from about .002" to .010" of runout.

I'm using a Hornady seating die, and have tried it in both a RCBS rockchucker and a Lee turret press. I put a good chamfer on the case mouth but it doesn't appear to help.


I have the same problem with my .223 loads that I am seating with a redding competition seater.


How can I reduce the runout introduced in the process of seating the bullet?

 

[RockZ]

It looks like your cases are good and straight. Are the case mouths square?

I was getting alot of runout when I tried a compressed load .
I then tried seating the bullet a little at a time and checked the runout at each phase .

I was getting very little runout through the first 3/4 of seating and then when I started to compress the powder I was getting the large amount of runout.
I haven't run compressed loads but wanted to try them.

It may help you to try seating and measuring runout on the way down to see where the runout is occuring.

It could be the press, the die, the way the die sits in the threads, even the shellholder can influence runout

If I'm seeing runout I don't like. I seat by carefully aligning the bullet and just barely seating it. Then I turn the case and seat it a little deeper and continue turning and seating until I have it fully seated.

 

[Buffalobob]

the way the sits in the threads

That's a problem I had. It took me four or five tries to get the die and lock ring square in the press. Maybe there is an easy way but I just kept unlocking and relocking and checking runout until I got it to where it seated bullets straight. Once you get it straight use the set screw to really lock the lock ring in place and it will pretty much stay that way in future uses.

 

[RockZ]

To keep a die square there are a couple of things you can do.

You can get a round and seat it nearly all the way and check that it is very concentric. If so, then run it into the seating die using it to put pressure on the seating stem and die and then tighten it down.

Another way for dies that don't have a sliding stem, is to put a washer on the shellholder and run it up to put pressure on the die and then tighten it down.

Depending on the type of die, the seating stem itself could be skewed and by putting a concentric round it the die and then tightening the seating stem can also help.

 

[Winchester 69]

Be sure the tip of the bullet is not contacting the seating stem. Mark the bullet with a felt tip to see where contact is being made.

 

[petenz]

Case mouths are squared with a wilson trimmer, and it's not a compressed load

I will try the things that have been suggested, thanks

 

[Winchester 69]

Seating in incremental steps, rotating the round at each increment, is a technique that many use.
Be sure that the bullet is straight at the initiation of seating.
.

 

[Ackley Man]

Try removing the snap clip that hold the shell holder and replacing it with the appropriate sized "O" ring this will let the case follow the die chamber in the event that the threads in the press are a little out of alignment.