Neck turning--wobble??

[Goatsnguns]

While turning necks on 20 VarTarg brass, that had been formed from once fired Lake City brass , this evening, I encountered a few that had quit a bit of wobble when chucked up. I am using a 21st Century case holder on a variable speed DC motor that runs true. I actually had no problem turning the necks as I "go with the flow" (wobble) and lightly hold the turner. I got to wondering why some of them wobbled, I took a close look at the few offenders and noticed that the rim of the wobblers had a high spot at one point. Probably due to a hard extraction would be my guess. I lapped the base of the case on a surface plate with 800 grit paper and it really showed up the high area. So much for why they wobble……..Now I am wondering how the uneven pressure from the high spot against the bolt face might effect accuracy when fired. Any ideas or comments? I sure hope this hasn't already been brought up before.

Thanks for any comments,
Gary

 

[Tim Singleton]

I would think that happened when first fired in the mil spec chamber. Maybe even machine gun brass. I doubt it's your chamber
Just a guess

 

[jonbearman]

What I do if I am reclaiming once fired, is I take my Wilson case trimmer and once the case is in the holder I turn it around and take a super light cut and then they are square and ready to shoot so to speak. To be clear I am only removing the high spots.

 

[Tim Singleton]

Maybe Biged will see this and put up some pics
Sounds like the case head is out of square to thie case from the original firing

 

[amlevin]

I see this on a few of the cases that were once-fired military like the LC.

I use a Sinclair case holder to turn mine using a low speed cordless drill. The one or two cases I encounter in a turning session that "wobble" straighten right up when fired in my rifle.

 

[BoydAllen]

Years ago, in a fit of OC behavior, I decided to try squaring up case heads on my Wilson trimmer. I did a few, and then noticed something. All of the cutting was starting in the same position relative to the trimmer, even though neither the cases and the holder were being indexed. Then the light came on. While sufficiently accurate to do an excellent job trimming cases, it was not a lathe. At that point I called Wilson to discuss it, not so much to complain, but to confirm my conclusion. They did not contradict my conclusion. Bottom line, if you are going to really square up case heads, some sort of late and appropriate tooling would be required, so that the case body is held coaxial with the axis of rotation of the spindle, and the case turns rather than the cutter.

 

[amlevin]

Bottom line, if you are going to really square up case heads, some sort of late and appropriate tooling would be required, so that the case body is held coaxial with the axis of rotation of the spindle, and the case turns rather than the cutter.

And in the end, how much difference will it make, if any at all?

 

[BoydAllen]

I have no idea. I don't have the proper equipment to do the experiment. If I was really concerned with the problem, I would probably build a gauge that was like part of the one that Creighton Audette used to sell many years back. It was designed to measure case head squareness.

 

[Tim Singleton]

Will they come square to the degree that his chamber and barrel are to each other when fired in his chamber?
Or are they just what they are ?

 

[BoydAllen]

I don't know, but I would think that a little testing would answer the question. If this was for a varmint rifle, I would probably use the wobblers for closer shots, and then reexamine the cases after they had been fired. I might also do a test with identical loads before taking them afield to determine if there was a difference in accuracy, and how much it was.

 

[pdog]

Why try to fix something that you do not know if it is a problem yet? You are doing the right thing by using the "go with the flow" method for neck turning. Keep a few of the wobblers separate and load them just like your other cases. Shoot them on paper and see if there is any difference from the the ones that did not wobble. My guess is that with a 20 VT you will not notice the difference. If there is a difference it will most likely be gone after the first firing. Use them for shots under 150 yards and they will be good to go on the second loading.
Jim

 

[Goatsnguns]

Thank you all for the comments & ideas.

I had purchased 200 pieces of 221 FB that was formed from LC 223 brass, that I was forming to 20VT, and had only three or four wobblers, not that significant. But just before I fell asleep that night, I started to think about uneven bolt pressure, stress on the case, accuracy, Etc.. But I think it will probably not amount to a hill of beans.

I form for two CZ 527's one with a standard .232 neck and one with a .228 neck. This batch is for the .232 neck and am still in the fire forming phase, I am getting good accuracy, so things are really looking OK.

I will post how they chamber and shoot, but I doubt that I will see much difference on the target. In the future I will examine the head squareness and rim deformation more closely before chuck'n them up in the case holder.

Thanks again for all the feedback, this is a great forum with a very deep knowledge pool.

Gary

 

[bigedp51]

Maybe Biged will see this and put up some pics
Sounds like the case head is out of square to thie case from the original firing

The extractor groove and outside of the rim of the .223/5.56 cases fired in a M16/AR15 rifle can get pretty chewed up. So any device that clamps on the rim of the case from a simple hand held Lee case trimmer or the far more costly 21st Century case holder will have case wobble with dinging up rims. And this is where a small fine file comes in handy to file down the dings.

Because of my two sons influences I now have more rifles that throw perfectly good brass away and torment my brass OCD. So either buy new Lapua brass without chewed up rims or spend more time tweaking once fired Lake City brass.

P.S. They have another new fangled device called the Lake City chewed up rim eliminator that prevents "Neck turning--wobble??"
And the distance between your ears is also called headspace and the grey matter can be used for problem solving. (Posting score Enfield owner 10 - Benchrest shooters 0)

P.P.S. And one more thing, don't try and be a cool cat and listen to Rap music when turning necks. : (CatShooters biggest problem) :'(