Anyone know what part of a cartridge case grows?

[Bmi48219]

Just read the "my 45 set up...." post and it occurred to me some forum members may be able to set me straight. Once in a while I get a piece of brass that won't slide into the shellholder. No big deal, lots more to reload. My experience that prompts this post is with 30 carbine USA headstamp brass. I've learned that any brand of 30 carbine brass grows. I have to trim 12 to 15 % of my resized 30 brass, regardless of HS, every time I prep cases.
I prime with a Lee Bench primer, the one that uses special, can't be used for anything else, shellholders. I've noticed one out of ten pieces of USA 30 brass won't fit into the shellholder. I pitch those but next time I'm priming there are more that won't fit, even though they fit last time.
I believe this particular shellholder is machined to fit pretty tight. But I've never had any other brand of brass (LC, Starline, Remington, Winchester, etc.) fail to slide into the holder & some have been reloaded 8 or 10 times. I should add that these are mild loads, at 13.7 grains 4227, easily a full grain below max, meant to reduce wear & tear on my firearms.
I always assumed brass growth occurred in the case wall. But I think in this brand the extractor groove is either getting tighter or growing forward from the rim.
So has anyone out there ever investigated where brass growth occurs, particularly in a slightly tapered case? Or why else would cases that fit the last time primed not fit again?

[Artful]

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[triggerhappy243]

you need to inspect the condition of the shell base and the rim. it may be bending upon extraction.

[str8wal]

I have bought fired brass that has had some burrs on the rim of the cases that would hamper insertion into a shellholder. I think some guns are hard on the rim during extraction. Might be worth a look.

[country gent]

Semi autos get pretty violent in the extraction of cases, Especially military versions since they are more concerned with function not reloading. Check to make sure rims arnt bent or out of square. The cases expand in the solid head depending on pressure and flow forward since this is the only direction it can move. Pressure can be compared measuring the same brasses case head expansion from factory loads to hand loads with a good michrometer even.
On the 30 carbine ( especially id fired in the M1 carbine) I suspect the problem cases are due to slightly bent pulled rims.

[robg]

Had that problem with some 308 brass .took an non fitting case and tried it in another shell holder ,it went in easy (lapur brass) just an undersized shell holder .

[n.h.schmidt]

I have had the same problem with 45acp cases. I do not load hot most are medium loads. I have some cases that have been loaded over twenty times. With these cases even the head stamp has been worn off. The rim dia with many of these cases needed filing to allow them to fit in the shellholder.
n.h.schmidt

[Bmi48219]

All good suggestions but still comes back to: why does it only happen with USA brass? I found a couple hundred of them last year at the range. Been reloading LC, R-P, Winchester, Federal, Top Shot, S&B & Aquilla for several years, never a problem with them fitting the shell holder. I have a pile of deprimed 30 carb ready to clean & process. I check case length after sizing, am sure some USA's will be in the too long bin. Also, sure some of them won't fit the shell holder. I'll examine the rim area on them and post my observations.
My carbine only comes out 3-4 times a year. I feed 100 rounds through my AMT auto weekly.

[mdi]

Another idea. I read once that semi-auto brass actually shrinks at the case head. The repeated banging against the bolt upon firing can compress the extractor groove...

No 30 Carbine use here, so I can't comment on that.

[gwpercle]

Manufacturing tolerances and differences...between shell holders and brass...it all adds up.
While resizing some mixed 9mm luger once fired brass I would find the occasional shell that wouldn't go into the Lee shell holder, so I would put them in a container for later. Later , After working on the extractor grooves with a Swiss file ...making them wider/deeper...I realized some had ever so slightly protruding primers...it was the primers that kept the brass out of the shell holders.
Now the 9mm is a fairly high pressure round, never noticed this with 38 special or 45 acp. low pressure.
That 30 carbine is a high pressure round also....give those primers a close eyeballing and make sure they aren't poking out just enough to stop it from going into the shell holder. Sometimes it's just a raised crater around the firing pin mark that stops them from entering .
Some shell holders are made with a little trough (groove) right where the primer passes ( Lyman, CH4D , Redding ) ...but Lee shell holders do not have this trough....any primer protrusion will stop them from sliding in. The primers that are protruding I just seated deeper, those with a raised crater around the primer hole...I filed off...
Then every one slipped into the Lee shell holders...check the primers or get a shell holder that has a little groove machined into it for the primer clearance.
Gary

[jsizemore]

Maybe you could have a xrf comparison of cases to check material composition.

[Bmi48219]

Gwperle, this occurs when I try to insert cleaned, sized & trimmed USA 30 carbine brass into the Lee bench primer so I can prime the case. It's not a show stopper, I have plenty of brass, if the case won't fit into the primer shell holder I just pitch it. Just thought it was odd it only happens with one brand of brass. I'm thinking USA brass has a different metallurgical composition.

[Bmi48219]

My reason for starting this thread was to see if anyone knew what part of the case actually grows.

[Artful]

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[Artful]

My reason for starting this thread was to see if anyone knew what part of the case actually grows.

It depends upon the case / chamber - lots of bottleneck cases seperate above the base because the neck/shoulder is firmly held and the back of the case moves back until stopped by the bolt.



I've had it in some rimmed cases as well - but one handgun usually separated at about the half way point on the cases.

[flashhole]

Artfuls pics tell the story for bottle neck cases and answers the question - what part of the case actually grows (or stretches and thins the case wall). I've seen the same in 30-30 rimmed cases. What it underscores is the practice of not overworking the brass by total FL resizing. Get to know your guns chamber dimensions and size brass so it only bumps the shoulder back ~.002", enough to allow it to chamber but not so much as to have brass flow out the neck and get trimmed off.

[Bmi48219]

No shoulder on a 30 carbine, but case is slightly tapered. Head spaces on case mouth so I trim to .005 " short of the 1.290" max case length.