Reducing Case Stretch and Runout

[BJung]

I carefully trimmed my brass to the same length and after neck sizing them, the brass stretched .005" using Imperial Die Wax as the case lube. Is that common?

I then used an RCBS .310" neck expander plug to expand the case neck to the same dimensions. I used Imperial Die Wax again to lube the case mouths. After charging the case and seating a bullet, I had a lot of Runout. When I had a Custom Lee Collet Die, runout was almost zero. How much will runout ruin my test load results at 300 yards?

 

[stringnut]

Not quite sure I understand your process. Are you neck sizing without an expander plug? What kind of dies are you using? Trimming is done after sizing operations. How are you expanding the necks? What is “a lot” of runout? Dad clarification to even take a guess.

 

[lordpaxman]

It’s common to have neck sizing stretch brass. It’s also common to trim to length after sizing.
I use the Imperial graphite neck lube, not their wax. Although, I can’t imagine the lube causing a problem with runout. As to the effects on target, well, I wouldn’t hazard a guess. Good luck.

 

[Blue68f100]

I do not like any run out greater than 0.002". Most all of mine is 0.001" or lest on my match grade ammo. I FL size all my brass, NS adds more changing variables with every load. If by chance you have brass that was not fire formed in your gun your compounding the problem. Neck thickness not being the same all the way around can also cause the alignment to move.

When I have some that are off, I normally run them back through a FL sizer again after annealing. This normally straightens the necks back out.

 

[edwardware]

. . . and after neck sizing them, the brass stretched .005" using Imperial Die Wax. . .

I think "stretch" might be deceiving you. The brass didn't grow because you pulled it out of the neck sizer hard enough to elongate it. It grew because you pushed it into the neck sizer, and the brass displaced by reducing the neck diameter had to go somewhere. That somewhere is an increase in length and wall thickness, but mostly length.

Generally, trim after your sizing operations are complete.

 

[jmorris]

I carefully trimmed my brass to the same length and after neck sizing them, the brass stretched .005" using Imperial Die Wax as the case lube. Is that common?

The case is “blown out” to fit the chamber when fired, a size die ensures it is brought back to a dimension that will chamber again. Making the OD of the case smaller is what forces material up from the base, this is what you are trimming. It is the sizing process that make them longer not firing them.

This is why the most trim AFTER resizing the case. If we don’t size them first, we can’t ensure any specific length. Cut them after sizing and they will all be the same.

 

[AJC1]

The Lee die uses a precision mandrel that uses your primer pocket for concentric alignment. Your neck sizer may not be aligned correctly and might not have anything to index off. I like a standard full length die because the neck is reamed concentric with the body of the case. Bushing dies float so induce more runout imo.

 

[jmorris]

After charging the case and seating a bullet, I had a lot of Runout. When I had a Custom Lee Collet Die, runout was almost zero. How much will runout ruin my test load results at 300 yards?

Runout is best eliminated by testing your round before and after each and every step. This eliminates guessing where the problem starts.

For example, above you say AFTER charging and seating, you had a lot of runout. That’s leading me to assume the case was OK before you seated the bullet. If that is true, the case made it out of the size die without run out and seating the bullet is where things went wrong unless your damaging the case putting powder into it.

“How much effect at 300 yards?” Is an unanswerable question as that is firearm/load dependent. We don’t even know what you and your firearm can do at 300 yards with perfect ammunition.

One that perplexed me was one load I have for a particular barrel that just doesn’t come out of the press perfect but it shoots ~ 3/8”, 5 shot groups at 100 yards. I always scratched my head as to why it shot so well when I knew they had runout and one day I checked them before and after chambering (not firing) in the barrel and discovered the runout was corrected when the chamber was closed on the round and the bullet contacted the lands.

 

[JFrank]

I carefully trimmed my brass to the same length and after neck sizing them, the brass stretched .005" using Imperial Die Wax as the case lube. Is that common?

I then used an RCBS .310" neck expander plug to expand the case neck to the same dimensions. I used Imperial Die Wax again to lube the case mouths. After charging the case and seating a bullet, I had a lot of Runout. When I had a Custom Lee Collet Die, runout was almost zero. How much will runout ruin my test load results at 300 yards?

I have never been able to see the difference on paper in cases that display any run out and neither has anyone I know, as J morris points out the chamber corrects the round

 

[jmorris]

I don’t know what equipment you are using to measure with but some are only really useful for loaded rounds.



They can be quicker and easier to use but due to points of contact they don’t give you the same readings as other methods.

Others can be adjusted to different points of contact body/shoulder and measure the case itself empty before and after the sizing process, then adjusted again to measure the completed rounds.



And it your having to trim that much off the case every time your firing them you might also want to start checking for wall thickness before you start having head separation and that can be done with some too, making the tool even more useful.

 

[jmorris]

…as J morris points out the chamber corrects the round

I didn’t intend to say it does but I do know than it can and you won’t know until you check.

 

[JFrank]

I’ll say it myself, there just isn’t enough clearance in the chamber unless the smith was totally incompetent.
Fired rounds are normally concentric.

 

[Walkalong]

From a good chamber

 

[AJC1]

I will agree that chambers can help rounds with run-out, but I believe that to be most effective at some depth into the lands. There seems to be a lot of fear surrounding those loads and I find it strange. Wobbly rounds slammed into the lands at high pressure can't help bullet rotational ballance.

 

[BJung]

I have more test loads to assemble so I will try replacing my decapping pin and ball with a smaller caliber sized ball that that the primer will removed and neck expanded with a well lubed neck expander plug. I'll do this in two weeks since I'm going fishing this coming weekend. I didn't think about trimming the cases after resizing this set because I wanted to leave the primers inserted so I could fill the cases and determine their volume. I'll resize the cases differently the next time. Right now I'm leaning towards buying another Lee neck collet die when available.

 

[BJung]

I don’t know what equipment you are using to measure with but some are only really useful for loaded rounds.

View attachment 1069002

They can be quicker and easier to use but due to points of contact they don’t give you the same readings as other methods.

Others can be adjusted to different points of contact body/shoulder and measure the case itself empty before and after the sizing process, then adjusted again to measure the completed rounds.

View attachment 1069003 View attachment 1069000

And it your having to trim that much off the case every time your firing them you might also want to start checking for wall thickness before you start having head separation and that can be done with some too, making the tool even more useful.

View attachment 1069001

Nice homemade setup! I am using a Sinclair Concentricity gauge.

 

[jmorris]

There seems to be a lot of fear surrounding those loads and I find it strange.

There are a number of people that do it and don’t even know. Especially with ELD’s these days.

Factory Hornady 6mm cm on right, after being chambered in Ruger rifle center (tip deformation caused by removal from bore). Left is one pushed back to the point of just contacting the lands.

Ruger had the rifle back twice to fix the problem and didn’t. Wound up “up grading” him to their precision rifle and the bullets are also in contact with the lands upon chambering.



I told him at the time I would have kept the first rifle as it did shoot better than any Ruger I had played with.

Who knows how many others are out there under similar circumstances. Only someone familiar with the concept (likely a reloader) would even know to check. Others might not even notice unless it’s an extreme example like above where an unfired bullet is pulled from the case upon extraction.

 

[jmorris]

I am using a Sinclair Concentricity gauge.

It will work on empty cases as well as loaded rounds so you can check a test batch all the way through.

You can also segregate rounds that happen to come out perfect from “awful” ones. Then go to the range yourself and see if it is something worth being concerned about, with your setup.