Runout?!

[Forester]

I have all of a sudden developed a problem with high runout in my reloads. I used to get very consistant .003" or less with many coming in at .001" or so.

Nothing has changed as far as brass or preparation goes. My cases have .001" or less after they are fully prepped but when I seat a bullet it comes out with .006"-.007" runout. I usually use a Redding competition seater die and I have also tried a standard Redding seater die with the same results.

The press is a Forster Co-Ax and is fairly new and in good shape. I cleaned up the dies well as well as the press, and nothing seems to help.

Anyone have any suggestions about what else to look at? I am out of ideas except to try another press in case something has gotten tweaked about mine.

Before it is even said, I have proven to my satisfaction that runout over .002" does matter, and it matters more the longer the shot.

 

[ss7mm]

Is it the same seating die as before?

Are you using the same bullet as before or a different bullet?

Reason for the questions is, have you checked to make sure that the tip of the bullet is not being hit by, or bottoming out in the seating stem? You'd have to take the seating stem out to check but if the die/bullet combination is the same as before then this probably wouldn't be the problem.

Do you have measured dimensions of the case necks after prep in the before instances? Do you know the neck thickness before and now? Do you have before and now dimensions of the case neck prior to seating and after seating? Just curious as to whether anything in the neck area has changed. How many reloads on the brass?

And I'll agree with you on the runout. I try and keep mine as low as possible.

 

[Forester]

Is it the same seating die as before?

Are you using the same bullet as before or a different bullet?

Reason for the questions is, have you checked to make sure that the tip of the bullet is not being hit by, or bottoming out in the seating stem? You'd have to take the seating stem out to check but if the die/bullet combination is the same as before then this probably wouldn't be the problem.

Do you have measured dimensions of the case necks after prep in the before instances? Do you know the neck thickness before and now? Do you have before and now dimensions of the case neck prior to seating and after seating? Just curious as to whether anything in the neck area has changed. How many reloads on the brass?

And I'll agree with you on the runout. I try and keep mine as low as possible.

I discovered the problem as part of a test to see if neck turning would improve on already low ES. I am using Lapua cases, the neck turned cases had a .014" thickness and the unturned cases ran .015-.016".

I am using the same bullet as before, Berger 168gr VLDs (.308) I ran out of the old lot, so this is a new lot of the same bullet. Bullets are sorted by bearing surface length.

The bullets do not bottom out in the Redding competition seater die, I am not sure about the standard die but I got similar runout readings from both so I am leaning towards ruling out the die.

I think I am going to borrow a friends press and load a few with my dies, if I get low runout on his then I am stuck blaming the press even though I can not figure out how that would have happen.

FWIW, on 20 neck turned cases, 18 had .006" runout and 2 had .007", very consistant and maddening!

 

[britz]

are you Partial full lenght resizing, full length sizing or neck sizing? Is it a factory chamber. The reason I ask is I have a rem 700 30-06 with a chamber and bolt that are not centered, neck sized cases have a bulge in them which I think could affect runout. However, this wouldn't explain the change in runout for you.

 

[AJ Peacock]

Is this the first reloading after neck turning?

Did you resize after turning?

Could something in the turning operation have 'tweaked' the necks?

AJ

 

[Buffalobob]

Have you annealed the necks?

 

[Forester]

I am using Lapua cases that have been fired either 2 or 3 times depending on which lot, both lots yeild the same result. Cases have not been annealed.

AFTER the cases are fully prepped, I have less than .001" runout on the neck so I believe the problem is not in the prep. Cases are neck sized only with a Lee Collet die.

The neck turned cases were turned, fireformed, turned again and loaded, resulting in incredibly consistant .006" runout. If I only had the problem on neck turned cases I would blame my in-experience in neck turning, but I get the same result from cases that have never been neck turned.

Factory Savage chamber and barrel.

Loaded rounds that I put together a week and a half before these show very low runout. The problem seems to have come on all of a sudden.

I am going to do some measuring on the press and see what I come up with.

 

[britz]

keep in mind, if you are measuring runout at the middle of the neck on the case and at the tip of the bullet for the loaded cartidge, the neck runout will multiply by a few times by the time it gets to the tip of the bullet.

 

[NesikaChad]

I have all of a sudden developed a problem with high runout in my reloads. I used to get very consistant .003" or less with many coming in at .001" or so.

Nothing has changed as far as brass or preparation goes. My cases have .001" or less after they are fully prepped but when I seat a bullet it comes out with .006"-.007" runout. I usually use a Redding competition seater die and I have also tried a standard Redding seater die with the same results.

The press is a Forster Co-Ax and is fairly new and in good shape. I cleaned up the dies well as well as the press, and nothing seems to help.

Anyone have any suggestions about what else to look at? I am out of ideas except to try another press in case something has gotten tweaked about mine.

Before it is even said, I have proven to my satisfaction that runout over .002" does matter, and it matters more the longer the shot.

.001-.003 suddenly jumping to .006-.007 is pretty significant, over a 100% increase.

Brass, like almost all metals has a certain degree of spring to it, it has to otherwise it'd never come out of the chamber after firing it. So, your brass has to be "influenced" more than just .007" for it to have a TIR of .007" I'd say on a guess its probably more along the lines of .015 or .020. Just a guess, I don't have any real way of knowing.

So, where in the operation of loading a case is sufficient force generated to cause this much defelction? I'd say two; sizing and bullet seating.

You stated that the case looks pretty good once its all prepped. That it isn't until after the bullet is seated that things get goofy. Here's where I'd focus the attention then.

This also eliminates the press I think because the problem should have surfaced during sizing as well.

Back to seating. I guess make sure the shoulder isn't banging into the die. use some prussian blue high spot indicator on the case shoulder and see what's going on. Make sure your case mouths are chamfered, especially if using a flat base bullet. Make sure seating depth isn't so great that its crushing (crunching) powder and causing you to use excessive force when seating the bullet. Make sure you have the right neck sizing bushing (if your using one) in your sizing die and that you are not overworking your brass and causing a partial shoulder collapse when seating the bullet from excessive neck tension.

This is where I'd focus my attention.

Thats kind of the problem with these bullet/case runout gagues, they tell you something is up, but don't really show you where.

Do you use a neck mandrel? Sinclair International sells a nice set up that will straighten necks on new brass. I do this on all my cases prior to loading since its so easy to ding a case mouth and cause it to go out of round. Might look into one, they don't cost too much and you can buy (or make) arbors for different calibers. Very handy tool.

Good luck.

C

 

[NesikaChad]

Neck turning

I should have read the whole thread before responding. Lets look at this from a machinist perspective.

We have a barrel with a chamber machined in the back of it. We want to believe that the theoretical centerline of the chamber is on the same centerline as the rifle barrel bore. This means the chamber and bore are very concentric with one another. The "DATUM" or point of origin on all this is that theoretical bore centerline. Everything is based off of that.

Ok, skewelsz out, go play.

Not so fast.

Now we take a piece of brass formed into the shape of that chamber with a 40 ton press. If we put the brass on rollers and then place an indicator on it, it has very little runout telling us that the outside is indeed pretty round.

Now chamber that brass. The OD of the case is pretty concentric to the bore because that is what it registers on when the gun goes into battery. The few thousanths of slop between the case and the chamber take some of this away, but its not much.

I'm interested on what goes on on the inside of the brass. Short of splitting cases in half and measuring wall thickness, we just don't know, and this is where you may be finding some of the problem. The other part may be in your inspection equipment.

If your using calipers to measure wall thickness on a round (tubular) surface your wrong. The caliper jaw on the outside runs to the tangent of the arc however the inside jaw is catching the edges and throwing the dimension off. Smaller the case neck, the more pronounced the error becomes due to the tighter radius.

A micrometer built for measuring wall thickness on tubing is what should be used. Starrett makes a nice one for less than $200 dollars.

The typical neck turning tool uses an arbor to locate off the inside of the case neck. We assume that the inside of the case neck is concentric with the outside, but if it isn't all we are doing is making the neck a uniform wall thickness with no consideration as to how it relates to the rest of the cartridge.

This is why (and I realize its not in everyone's ability to do this) I use a tool room lathe with a 5C "emergency collet" "chambered" to the cartridge I am neck sizing. The case is supported on the outside and the necks are turned so that they stay concentric to the outside body of the cartridge. It's a real, real, real pain in the arse to do it this way, but it does do a pretty nice job.

Make sense?

I realize I really haven't answered your question and may have only added to the confusion. Lapua brass is renowned for being top shelf stuff, so I would certainly invest the time to ensure the other things mentioned aren't going on before thawing out the Visa on a 20K Hardinge tool room lathe.

Good luck, tell us what you come up with.

Cheers.

C

 

[boomtube]

"... the neck turned cases had a .014" thickness and the unturned cases ran .015-.016"."

Your neck turning has increased the sloppy fit of the necks in the seating die, making it possible for the cases to be pushed further to one side as the bullets enter the neck. No "seat part way and turn 180 degrees to complete" will help, the case slop will just move to the point of least resistance again.

It may be that you would correct the problem by using a Lyman "M" expander die. That excellant expander pretty well insures that the case flare - for easy bullet entry - is consistant around the circumference of the mouth. A consistant mouth flare helps center the case neck in the seater too. I love the "M" dies for all my reloading needs.

 

[Winchester 69]

It seems that the one variant from what used to be to present has been the new batch of bullets. It hasn't been stated; is the diameter of the old different from the new? What I am thinking is that the new bullets are marginally larger than than the old. If the inner chamfer of the brass doesn't align the bullets adequately, this condition coupled with an increase in bullet diameter might possibly cause the problem. Since you are using the Lee collet die, you don't have the capability to easily compensate for the interference fit of the brass and bullet.

My thoughts. Perhaps some new areas for experimentation.
.

 

[Forester]

It seems that the one variant from what used to be to present has been the new batch of bullets. It hasn't been stated; is the diameter of the old different from the new? What I am thinking is that the new bullets are marginally larger than than the old. If the inner chamfer of the brass doesn't align the bullets adequately, this condition coupled with an increase in bullet diameter might possibly cause the problem. Since you are using the Lee collet die, you don't have the capability to easily compensate for the interference fit of the brass and bullet.

My thoughts. Perhaps some new areas for experimentation.
.

Maybe I am dense, can you expound on this a bit? I honestly don't know, and have no way of knowing now if there was a change in bullet diameter, but how would this change runout numbers?

Both batches of bullets are .308 Berger 168gr VLDs. I have been out of town all weekend but will do some more looking based on the above posts and post back what I find.

 

[Pdvdh]

Pretty weird for your runout to go to the dogs all of a sudden. If I read right it only began after you outside neck-turned your brass correct? I'll keep following your thread as I'm interested in learning what the culprit is/was.