Why excessive runout on some rounds?

[RABAZ]

Using a Hornady single stage or a Dillon 550 progressive, with a Forster micrometer seating die. Making me crazy. I'll get most loaded rounds at .003 or less runout, but will get occasional at double that or more. What gives? Pretty deliberate about my loading process and careful, so don't understand what, if anything, I'm doing wrong. Any insight appreciated.

 

[HSmithTX]

What brass are you using, and how many firings on it? Has it been annealed? Are you full length sizing or neck sizing? If full length how much are you bumping the shoulder when you size? Is the whole bullet off axis or is the bullet crooked in the case? Meaning do you get 6 thousandths runout at the case mouth and near the tip of the bullet? Lots of things can contribute to runout.....

 

[Justice1327]

Try spinning the loaded round 180degrees and seat the bullet again

 

[RABAZ]

What brass are you using, and how many firings on it? Has it been annealed? Are you full length sizing or neck sizing? If full length how much are you bumping the shoulder when you size? Is the whole bullet off axis or is the bullet crooked in the case? Meaning do you get 6 thousandths runout at the case mouth and near the tip of the bullet? Lots of things can contribute to runout.....

PPU brass - I keep brass grouped by # of loadings. FL sizing only, bumping shoulders a couple thou. Trim all same length. Haven't checked both at bullet tip and case mouth. Will do. I do rotate cases and "seat" 3 times.

 

[Barrelnut]

Also good idea to check the neck runout on the case neck after resizing it and before you seat a bullet. Seperate the ones with excessive neck runout after sizing. This way you can figure out where in the process the problem is happening.

 

[HSmithTX]

Also good idea to check the neck runout on the case neck after resizing it and before you seat a bullet. Seperate the ones with excessive neck runout after sizing. This way you can figure out where in the process the problem is happening.

This is great advise, if you don't see any runout in the sized cases mic the neck thickness and make sure it is fairly consistent, if the brass is heavy on one side there isn't much you can do to eliminate the runout it will cause other than neck turning, I personally would replace the brass long before neck turning if using a chamber reamer that isn't intentionally set up for neck turning.

 

[Ol' Red]

Tagging in

 

[Wallrat]

Ok. I'll be the dummy here who has to ask: what exactly is "runout"?

 

[RABAZ]

How much the bullet is "crooked" in the case.

 

[Hugnot]

I like to anneal & F/L size with expander & turn necks & then F/L size without expander. A good seating die will not fix a "crooked" neck.

 

[Hard rock]

How much the bullet is "crooked" in the case.

I would go too a bushing die and get rid of the expander button, that way you can control neck tension and if everything else is the same neck thickness etc the only run out you can get is in the seating process .The Redding comp seat die and Forester are great seat dies.

 

[Hard rock]

I would go too a bushing die and get rid of the expander button, that way you can control neck tension and if everything else is the same neck thickness etc the only run out you can get is in the seating process .The Redding comp seat die and Forester are great seat dies.

.003 runout is not bad but .000 is definitely what we all would like too see. I have tried about every trick in the book , it can drive you nuts , My above post is how I do it after many years trying different methods.

 

[rellim8154]

Use of an le wilson mandrel die is great for uniformity of the inside dimension of the neck. Creates consistent neck tension on the head.
I bump the shoulder 2 thou in a full length sizing die, with the spindle and ball removed. Then the mandrel for the neck.

The fl sizing die with the ball and spindle opens the neck on the down stroke, then the die closes it, then as the ball comes back up it re opens the neck. This works the brass more and can un do some of your sizing based on how hard or soft the brass is. Brass if over annealed can get "springy"
The LE wilson mandrel die is great after initial cost, it's $18 for different caliber insert. And it has a window for lube, just a squirt and I hold a rag under for a few seconds.

 

[choprzrul]

I've gotten to where I remove the neck sizing spindle from my FL dies and just deprime by hand. Bump the shoulder back 0.002-0.003" and then use a Lee collet type neck sizing die. Trim/chamfer the case to length, prime, and then seat the bullet with a L.E. Wilson chamber type seating die: https://lewilson.com/chamber-type-bullet-seater

Not perfect, but good enough for my hunting rounds....