Why excessive runout on some rounds?

[Barrelnut]

If your cbto is also varying then your forster micrometer bullet seating stem is messed up.

Forster stems are extremely fragile.

Get rid of that die and get a redding micrometer seater if that's the case.

Good point. This is particularly true of older Forster seating dies. The cup of the seating stem is thin and can get a hairline crack on the side that results from excessive pressure seating a bullet. It is hard to see and can cause CBTO issues and possibly runout too. You can often feel the crack with your fingernail. You can order an new one from Forster. The newer ones are thicker in the cup area which resolves the issue. Both Forester and Redding seater dies are excellent but the tip of the hat goes to the Redding.

 

[Greyfox]

I see the occasional round that runs high every once in a while. My standard is <.002". I just use the pressure screw on the Hornady gauge to get it back down to .002". It works well. Testing these corrected rounds indicates that performing this adjustment does not effect accuracy, ES, velocity, etc.

 

[.300 Dakota]

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.

I find this about impossible to control using most Hornady, Remington, Winchester, and Starline brass. Usually not a problem with Nosler, Norma, Lapua, or ADG. No experience with any others. I think it has more to do with the condition of the brass itself around the neck/shoulder junction. Sometimes turning it 90 or 180 degrees and resizing pulls it back in spec, sometimes not. FL sizing is worse than neck sizing for this phenomenon.

 

[dougduey]

One thing that really improved my concentricity and lessened run out was seating my bullets to where the base or boat tail/base junction was even with the neck/shoulder junction of my brass.

 

[Barrelnut]

Compressed loads have caused me runout issues. I really try to avoid them.

 

[dougduey]

Compressed loads have caused me runout issues. I really try to avoid them.

Good point and why I try to avoid them, too

 

[Mr. Magoo]

I have never been extremely happy with any of the reloading dies I've come across. It's been something that has bothered me for years and I'm finally doing something about it.

I'm in the process of designing and testing a new style of dies that don't *allow* for any apprecialble runout during the sizing and seating process. These won't be for your average reloader, as it requires a special press to work with the dies, and are not going to be cheap, but it takes any variability in style or brass inconsistencies out of the equation. These are still a ways out from being something I can sell.

For normal dies, there are a few steps I take to make sure its not something simple throwing it off. You probably have all this covered but just to throw it oit there:
Make sure your shell holder is dead flat in relation to your die using a feeler guage (I've seen shell holders improperly machined), and that there's no junk buildup on top the shellholder pressure surface.

Beveling the case mouth is obvious but some chamfer tools will create another burr inside after you use them so check that the inside of the case mouth is perfectly smooth and that the bevel is concentric with the case mouth. Use a ball mic to measure case mouth for consistent thickness in 3 or 4 spots.

Make sure there's not a bit of junk in your seater nose or inside your seating die. Basically if your bullet starts in crooked or the seating pressure is off center from the centerline axis of either the case or the bullet, there will be runout as the case neck isn't strong enough to 'force' the bullet straight after starting in crooked.

 

[WildRose]

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....

Give one of these a whirl, it just adds one more step.

DECAPPING DIE | Brownells

The Lee Universal Decapping die is made of steel and designed to allow shooters to decap cases without the need of lube or cleaning. Guaranteed by Lee as unbreakable. Easily removes crimped-in primers. Fits cases up to .550”, not recommended for u...

www.brownells.com

I started using these, neck turning, and a bushing die and boy did it make a big difference.

 

[WildRose]

Good point and why I try to avoid them, too

The bullets also tend to walk back out of the case which is why I quit using compressed loads.

 

[deerhunt399]

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.

Try using Nosler or lapua brass never a problem with roundout in my experience

 

[Tulsa Reiner]

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

You aren't a dummy. I've always thought "runout" was a weird choice of words to describe a crooked bullet.

 

[Tulsa Reiner]

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.

I'm assuming you only turn the cases of your necks once in the life of each case?

 

[Dot_3]

Use of an le wilson mandrel die is great for uniformity of the inside dimension of the neck..

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.

Brass loses its springiness if it gets over annealed. It becomes soft and could potentially be dangerous due to its lack of elasticity. I believe in mandrels. Just another option for the OP, Sinclair, PMA, and I believe 21st century all make die bodies that will accept each other's mandrels.

My advice: put the gauge away and spend your extra time reading wind.

Like the man said, "Choot it!!!!"

 

[Elkaholic Hunter]

Give one of these a whirl, it just adds one more step.

DECAPPING DIE | Brownells

The Lee Universal Decapping die is made of steel and designed to allow shooters to decap cases without the need of lube or cleaning. Guaranteed by Lee as unbreakable. Easily removes crimped-in primers. Fits cases up to .550”, not recommended for u...

www.brownells.com

I started using these, neck turning, and a bushing die and boy did it make a big difference.

Looks like it's been stated but another plus one for removing the expander ball in your die, fl sizing then using an expander mandrel. This fixed runout in all my rifles.