What's Causing Bullet Runout

[Nvhunter92]

I really appreciate all of the help I've gotten from this website and I've found it to be a very good resource. I have a 7mm rem mag and I'm reloading with 162gr eld'x bullets. I'm using the rcbs gold metal match neck sizing and seating die set. My runout is under .002" after neck sizing but after seating the bullet my runout varies from .002-.006" within a batch of identically processed 30 rounds. What do you guys think might be causing this inconsistency? I don't turn my necks and I'm wondering if because I'm using a bushing die this might be the culprit but I'm not sure and have no way of measuring my neck thickness. I'm using nosler brass.

 

[adam32]

When seating bullets I always go up about 3/4 of the way go back down, turn the casing 1/4 turn then go back up all the way. Back down, turn another 1/4 turn and repeat 2 more times. Seems to work great to eliminate run-out.

 

[LaHunter]

I'm not familiar with that seating die, but if it is not made for VLD type bullets, that could be an issue possibly. I use the Redding Comp Seating die, even though I don't use VLD type bullets. I also use a technique similar to what adam32 uses.

 

[J E Custom]

I really appreciate all of the help I've gotten from this website and I've found it to be a very good resource. I have a 7mm rem mag and I'm reloading with 162gr eld'x bullets. I'm using the rcbs gold metal match neck sizing and seating die set. My runout is under .002" after neck sizing but after seating the bullet my runout varies from .002-.006" within a batch of identically processed 30 rounds. What do you guys think might be causing this inconsistency? I don't turn my necks and I'm wondering if because I'm using a bushing die this might be the culprit but I'm not sure and have no way of measuring my neck thickness. I'm using nosler brass.

Normally Run out Is caused by the reloading procedure. If the necks are not turned this can also cause run out.

Try loading using different processes and bullet seaters and test each one as you go to see which method gives you the best results.

Try rotating the case several times as you seat the bullet as mentioned. (Years ago, this was common practice when quality dies were in short supply).

J E CUSTOM

 

[Rich Coyle]

J E CUSTOM,

What are "quality dies"?

 

[Tesoro]

I dont think you should be measuring runout unless you also have a decent gauge to measure neck wall thickness!

Also you didnt mention anything about your case prep so lets start with this:

Think about it - if you have an uneven neck wall like 1.5 to 2 tho diff then when you size the neck you squash the unevenness to the inside while squaring up the neck to the case body via the die. And then you check your neck runout and its now passable of course. But then when you shove a bullet into that tight neck opening it is now not going into an even inside passageway so as a result the case neck is going to get slightly tweaked out of alignment with the case body. As the neck wall thicknesses can vary in a batch of cases you will find uneven runouts for that reason.

But beforehand you need to figure out your desired neck tension and use the correct bushing to get what you need based on the neck wall thickness. And you cant do this without having measured the neck walls!

I use a redding compet bushing die and get max .0015 runout but normally a tho or under. Redding wouldnt make them and we wouldnt use them if they caused extreme runout by themselves!

Once you have the case prep part all dialed in and still get unacceptable runout then can look at other culprits like uneven case neck lube (or not - I dont lube mine just brush them to get rid of any micro crud deposits). Also uneven or not sufficient chamfering after trimming. And then ensuring you have square ends on your neck. Alot of the 'decent' brand neck trimmers dont cut real square. If your neck isnt square then you cant chamfer evenly. I have found the wilson trimmer to work the best for me.

If you want to be splitting hairs on measuring runout then small things can make a noticeable diff. But in most instances its the lack of proper case selection and preparation that will make your gauge spike!

I dont agree on recommending neck turning as it can create more probs than benefits if you are not careful and very experienced. I dont mess with turning as I only use brass with a max 1 tho neck thickness variation but most of it is .0005 variation. Most real good brass is like this about .0005-.001 difference. I would only neck turn if my necks were that even but too thick to give my preferred bullet tension.

I use a coax press which they say helps with runout but I dont believe it when using compet dies. But I prefer that press for other reasons.

The #1 tip is what the above guys mentioned about about rotating when seating. I have had some that I measured a bit out of whack and even then put back in the press to straighten by rotating all over again. But the rotating tip isnt going to help much if your brass is not all square and even to start with.

Hope this helps.

BTW I am not a competitive shooter but some experienced LR shooters have told me that anything 5 tho and under dosent seem to make any big diff in accuracy taking into consideration all the other factors. But I look at runout as just another challenge to master in reloading. I can make consistent ammo much better than I can shoot the stuff!

 

[JakeM300winnie]

I ran into the same issues you are having loading 200 gr eld-x.I had standard rcbs dies.I went ahead and spent the money on the Redding bushing dies and competition seater and my problem went away.I'm pretty sure the problem was the long vld style bullets in the seater as Lahunter was saying.

 

[joep17]

Normally Run out Is caused by the reloading procedure. If the necks are not turned this can also cause run out.

Try loading using different processes and bullet seaters and test each one as you go to see which method gives you the best results.

Try rotating the case several times as you seat the bullet as mentioned. (Years ago, this was common practice when quality dies were in short supply).

J E CUSTOM

I like this advice. For competition rounds I use a Forester seating die. I try to do it in 3 steps by feel rotating it 1/3 per pull estimating how far I have seated the bullet.

I have an old RCBS tool that I though measured run out. It turned out that finger pressure changed results so I threw it in a box and have not looked at it again.

One thing I found is the old style pull through does a lot of neck distortion. Bushing dies always help and I think you are using them. I then use a PMI body with a 21 Century expander to try to get consistent neck tension and concentricity. Depending upon brass, neck thickness varies too. I try to neck turn all long range brass even if just to make it consistent and not to a reamer diagram....except for a specific match chamber.

Another thing I have forgot about for 30+ years. Around 1984 I got a buddy into reloading. He bought a new RCBS rock chucker presss. After years of poor results he sent it back them. Turned out the collet at the top was out of square and every round had unpredictable run out. They replaced it.

No idea how to check that but it as a problem for him.

So many variables that are hard to diagnose from the thread.

Don't give up and you will find the answer and get great rounds that shoot well. You will get posts based on problems we have encountered but hopefully no one telling you that you are wrong. This darn hobby is like trying to land on the moon. Hard to do but eventually you will do it.

Enjoy your quest for accuracy!

 

[243winxb]

Bullet seating pushes the flaws to the outside of the neck, same as an expander, when not neck turning.

Ok for factory chambers, if the whole neck is sized by the pushing.

If only sizing 1/2 of the neck, not a good thing.

 

[Tesoro]

Bullet seating pushes the flaws to the outside of the neck, same as an expander, when not neck turning.

Ok for factory chambers, if the whole neck is sized by the pushing.

If only sizing 1/2 of the neck, not a good thing.

why would you want to size 1.2 the neck?

 

[DUSTY NOGGIN]

I really appreciate all of the help I've gotten from this website and I've found it to be a very good resource. I have a 7mm rem mag and I'm reloading with 162gr eld'x bullets. I'm using the rcbs gold metal match neck sizing and seating die set. My runout is under .002" after neck sizing but after seating the bullet my runout varies from .002-.006" within a batch of identically processed 30 rounds. What do you guys think might be causing this inconsistency? I don't turn my necks and I'm wondering if because I'm using a bushing die this might be the culprit but I'm not sure and have no way of measuring my neck thickness. I'm using nosler brass.

with loaded rounds , concentricty gauge at the case neck place the vee at the middle of neck, then place indicator 3 places
1. directly over contact at vee , this measurement should be zero runout -- if you see runout here its your necks for sure ( mark the high and lows with sharpie )
2. vee still on middle of case neck, indicate right after case mouth on bullet ( as close to mouth of case without touching ) - this measurement will give a fairly consistent neck wall thickness - ( use the reference marks from measurement 1 , which normally will line up with out of concentricity measurement 2 )
3. vee still at neck center , indicate last available part of jacket on bullet - if 1&2 are fairly close and 3 is very out of wack , i might focus on changing your seating die type

i had a basic seater die ( no names to keep it isolated ) that threads for seater plug was not lined up to center-line of die body and would only seat concentric at certain seating depths ( twice every full rotation of seater plug adjustment rotation )

i think every type of die that has a one piece threaded seater plug , is susceptible to this type of failure

 

[243winxb]

why would you want to size 1.2 the neck?

The unsized part will fully expand to the chamber in 3 or more firings. This centers the round in the chamber. This works best with outside neck turned brass.

 

[bigedp51]

One of the biggest causes of neck runout is because the expander is locked down off center and pulls the case neck off center.

Below is a Forster full length benchrest die with a high mounted floating expander.
The expander enters the case neck while the neck of the case is held and centered in the die. Meaning this die can not pull the case neck off center, ensuring little to no neck runout.
These Forster dies make the most concentric cases of any standard type full length die I have ever used.

Below a Forster benchrest seating die that holds the case and bullet in perfect alignment. The Forster and Redding benchrest seating dies can even correct case neck runout to a certain degree.

Reloading: Seating Die Runout.
Seating Die Induced Runout - A Comparison by Germán A. Salazar.

https://www.google.com/url?sa=t&rct=j&q=&esrc=s&source=web&cd=1&ved=0ahUKEwi7n5W7-MnZAhXEzVkKHQ_xAAQQFggpMAA&url=http://www.uniquetek.com/store/696296/uploaded/Reloading-Seating-Die-Runout.pdf&usg=AOvVaw0PTrUzbIFGXpTquMkz6CtT

 

[Tesoro]

The unsized part will fully expand to the chamber in 3 or more firings. This centers the round in the chamber. This works best with outside neck turned brass.

interesting...I assume you are working with br tolerances and custom match chambers