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Old December 26, 2008, 12:16 AM   #1
antsi
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case trimming - strange case neck effect

Background info:

I am using a Lyman Universal Case Trimmer like this one:
http://www.cabelas.com/cabelas/en/te...equestid=76992
The cutter stays the same no matter what caliber you're using, but there is a small "button" or guide that goes in to the case neck to keep the case in position as the cutter is cutting. The button/guide comes in different sizes to fit the case necks of different caliber cases.

Caliber is .223

Brass: mixed head stamp, varying number of previous firings
(for my match ammo I keep all the same head stamp and all the same number of re-loadings. This is just some random brass I am loading up so I can shoot out at the farm, in the snow, or other situations where I won't be able to recover all my brass)

All of the brass has been resized in the same sizer die (.223 dillon full length sizer die)

The Problem:

Some of the brass seems to have a narrower case neck, such that the "button" or guide on the cutter will not physically fit down in to the case neck.

About 80% of the brass fits just fine.

I am not having this problem with the brass I have saved and kept track of for my match shooting brass.

There is no consistency in the head stamp or number of previous firings on the cases that don't fit on to the trimmer guide. Some of them are the same head stamp as my "good match brass." Some is Federal, some is Lake City, some is PMC. For each case that doesn't fit, I have some other cases with the exact same head stamp that do fit and function correctly in the trimmer.

The brass that won't fit is definitely .223, not some other caliber.

The guide is definitely the correct one for .223 case necks, and it fits all my good match brass and 80% of my mixed headstamp brass.

Does anyone have any idea what is going on here?

So far I am just setting aside the "mystery problem" brass and proceeding to process the other cases.
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Old December 26, 2008, 12:35 AM   #2
Scorch
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Sounds fishy. I use a Lyman Universal trimmer, have for 30 years. The pilot is designed to fit into a resized case neck. Once the brass has been resized (you are resizing before trimming, right??), the ID of the neck should be the same because you pull an expander ball back out through the neck. About the only thing hanging it up could be burrs (you are chamfering the necks, right??) or dings. If no dings/nicks/burrs, just push the pilot into the neck, don't be afraid to hurt it.
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Old December 26, 2008, 02:14 AM   #3
Lilswede1
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Noticed same thing

Just resized and trimmed a bunch of LC 223 brass and found the same thing.
Most fit on my RCBS Trim Mate just right but several were "tight" going on and coming off.
I can only attribute the difference in neck size to the "spring back" effect of brass.
I weighed the cases that were sticky and they were slightly heavier (.002 - 004") then the cases that fit correctly.
Loaded both with identical loads and will shoot them as soon as the snow clears enough to get to our range.
They loaded up fine.
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Old December 26, 2008, 06:12 AM   #4
Nail Shooter
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I have the same case trimmer and noticed the same thing in 223. Remove the case mouth button, spin in a drill chucked by its stem and polish its outside diameter down about .001" or so. End of problem. You're welcome.


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Old December 26, 2008, 06:52 AM   #5
antsi
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I think Shooter has hit the Nail on the head.
I was considering this polishing idea.
What did you use to polish? Emery cloth seems a bit too gritty. Steel wool? Scotch Brite? Those seem too wimpy.

LilSwede,
I tried "forcing" them. Some were so tight they would not stay clamped in the chuck. The ones where it worked, looked reamed out in the case neck and I was concerned may not be safe to shoot.
Weighing the cases was a good idea. My impression was that the sticky cases might be just ever so slightly thicker brass.

Scorch, yes, did resize first. Did chamfer/deburr.
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Old December 26, 2008, 08:49 AM   #6
PCJim
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How did that sticky brass feel when you were resizing the brass? Did you experience a similar stickiness when the ball expander entered and exited the neck? If not, then I'd agree that the diameter of the trimmer guide is a bit too large. You might want to check the diameter of both the expander ball and the trimmer guide with a micrometer.

On another note and I'm just throwing this out there as a wild hunch, is it possible that even with the same headstamp, you have collected some brass that was somehow weatherproofed with a sealant of some sort inside the case mouth that might be causing the problem?
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Old December 26, 2008, 10:03 AM   #7
DaveInPA
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Sounds like there may be a problem with your resizing die. They should all have exactly the same ID at the neck/mouth after resizing if your die is set up and working properly.
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Old December 26, 2008, 12:44 PM   #8
Lilswede1
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Polishing Guide

I tried using a fine emery board from wifes fingernail tools then finished it with steelwool. This worked great on several other areas that needed fine tuning on the press and several tools.
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Old December 26, 2008, 01:02 PM   #9
mkl
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Quote:
What did you use to polish?
I've had good luck with a fine valve grinding compound available at automotive stores. I have used it to lap bullet puller collets that would not release the bullet and on a few other things.

An even less aggressive alternative would be white polishing rouge if you have a buffing wheel and a bench grinder.
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Old December 26, 2008, 01:29 PM   #10
wncchester
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Lilswede is correct, it's due to varying springback of the older brass.

The sizer expander button is the same for all cases of course but springback of the older, work hardened stuff won't stretch as well as newer cases and the spring back is more, plus there is always a little thickening of necks as they are cycled thorough. That leaves you some slightly tighter necks. It's one reason to keep cases in batches that have been fired an equal number of times.

Annealing will solve the hardness problem IF you know how to do it correctly. Most folks don't, and that causes more trouble than it fixes.

Polishing/sanding the pilots down deals with the symptoms but doesn't correct the problem of your work-hardend cases.
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Old December 26, 2008, 01:59 PM   #11
antsi
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wnchester, your hypothesis fits the facts. The problem is only with brass of unknown origin and unknown number of previous firings. As I noted above, my own brass where I have kept them sorted by number of previous firings has not shown this problem.

If the cases are work-hardened and I am not going to anneal them, should I just call them scrap brass? This is only a small fraction, and it's my random throwaway brass anyhow, not my good stuff.

Am I likely to get split necks or other problems if I polish the pilot and reload them? What is the likelihood of a gun-damaging or shooter-damaging problem, versus simply having less accuracy?
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Old December 26, 2008, 02:26 PM   #12
rrp
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Lyman trimmer

I have trimmed thousands of 223 brass,mostly mixed headstamp,once fired surplus, with the Lyman Universal Trimmer, and have never had a problem like this. I too think it must be a problem with the resizing die. Let us know what you find out on this. Thanks
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Old December 26, 2008, 04:33 PM   #13
amamnn
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rebound or springback will not be the same for all necks, especially if you never made sure the neck wall thickness was uniform
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