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#3278183 - 06/09/21 08:38 PM Question on why my 243 necks are cracking
Dultimatpredator Offline
Die Hard Member III

Registered: 07/06/07
Posts: 2657
Loc: Wisconsin
To give the history on the brass it was given to me. I donít know how many times it was fired previously and how old it he brass is. I annealed all the brass about 2-3 firings ago. I am bumping the shoulders back approx 3000 thís. They are all RP cases. I trim the necks every time back to minimum length as most have grown during firing. I have fired them in two different BCA 243 uppers. They have been sized each time in my small base RCBS sizer die. Is the brass getting worked that much after 2 to 3 firings that they are cracking already? It seemed after every firing Iíve been loosing around 3 to Öor more, out of maybe 50 to 60 casings, to neck cracking. I would assume I need to anneal them againÖmaybe after every firing? I have shot 243 RP casings umpteen times my bolt actions and canít recall have a cracked neck in any of them.



I have the rest prepped ready to load. Iím wondering if I should anneal them before I prime and load? I always anneal before sizing the brass so itís kinda backwards. Just wondering if it will save a few cases by doing so?


Edited by Dultimatpredator (06/09/21 09:00 PM)

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#3278185 - 06/09/21 09:45 PM Re: Question on why my 243 necks are cracking [Re: Dultimatpredator]
Hellgate Offline
Die Hard Member

Registered: 08/28/12
Posts: 578
Loc: Orygun
I suspect the ARs basically have mil spec reamers for the chambers to ensure extraction. Mil spec is of looser tolerances so the weapon will continue firing under adverse conditions of dirt & combat grit getting into the chambers. The AR chamber necks are not tight benchrest necks and are letting the case necks expand more than your sporting bolt gun. The brass can't handle the stretching.

I had a similar problem years ago with a National Match .30-06 1903 Springfield that kept creating case head stretchings and partial separations. I took it to a gunsmith and he said the chamber was within SAAMI specs but .004 over exact so it would keep firing under less than ideal conditions: i.e. combat. He told me to not set the shoulders back as much and use a dedicated set of dies for that rifle and problem solved.

Your sizing die might need to be bored out a bit to prevent this over working of the case necks or just load up on brass and consider it the cost of using an AR.
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#3278189 - 06/09/21 10:29 PM Re: Question on why my 243 necks are cracking [Re: Dultimatpredator]
Dultimatpredator Offline
Die Hard Member III

Registered: 07/06/07
Posts: 2657
Loc: Wisconsin
My brass has a lot of deep scratches on the case necks. I wonder if the barrel lugs have burrs? Iíll have to see if I can lightly stone and polish the barrel lugs. I wonder if the deep scratches are making weak spots and causing the cracking?


Edited by Dultimatpredator (06/09/21 10:29 PM)

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#3278207 - 06/10/21 10:17 AM Re: Question on why my 243 necks are cracking [Re: Dultimatpredator]
WyoBull Offline
Seasoned Member

Registered: 08/25/11
Posts: 407
Loc: Wyoming
How hot is your load? I get neck cracks like this in all of my varmint rifles which are designed to shoot fast, like the 220 Swift or 17 Rem, after several loads have been through them. Annealing will definitely help but I don't expect to get more than 4, maybe 5 firings out of my varmint caliber brass.
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#3278210 - 06/10/21 10:44 AM Re: Question on why my 243 necks are cracking [Re: Dultimatpredator]
hm1996 Offline
PM Junkie

Registered: 07/23/06
Posts: 16739
Loc: S. Texas
Quote:
To give the history on the brass it was given to me. I donít know how many times it was fired previously and how old it he brass is.


If you can get some, I'd try shooting a few factory rounds, or known new cases (or even known once fired) and I'd bet you have no cracked necks. Old brass becomes brittle and are especially apt to crack when fired in "generous" chambers, as mentioned above. Unknown number of reloadings + older brass would be my guess.

Regards,
hm
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#3278225 - 06/10/21 08:51 PM Re: Question on why my 243 necks are cracking [Re: WyoBull]
Dultimatpredator Offline
Die Hard Member III

Registered: 07/06/07
Posts: 2657
Loc: Wisconsin
QUOTE

How hot is your load? I get neck cracks like this in all of my varmint rifles which are designed to shoot fast, like the 220 Swift or 17 Rem, after several loads have been through them. Annealing will definitely help but I don't expect to get more than 4, maybe 5 firings out of my varmint caliber brass.
_________________________
)))))>>> Old cowboy wisdom... "Lead in the air... maybe. No lead in the air... no maybe" <<<((((((

QUOTE



They were 55 grain NBTs shot at max loadings.


Edited by Dultimatpredator (06/10/21 08:52 PM)

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#3278274 - 06/12/21 08:15 AM Re: Question on why my 243 necks are cracking [Re: Dultimatpredator]
Dultimatpredator Offline
Die Hard Member III

Registered: 07/06/07
Posts: 2657
Loc: Wisconsin
I took a file and lightly went across all my barrel lugs. Then I polished them with a Dremel tool and mothers chrome polish. The scratches I was was getting on the case neck area is now very light on a few to non existent now on others. It went from light scratching to completely disappeared after shooting a few groups.

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#3278397 - 06/17/21 11:25 AM Re: Question on why my 243 necks are cracking [Re: Dultimatpredator]
spotstalkshoot Offline
Die Hard Member III

Registered: 12/22/13
Posts: 2135
Loc: so.mn
The 3rd,4th from the right don't look like they have even been sized/fired. Shoulder and neck not formed like the rest, What are the neck numbers? Especially neck wall thickness, old brass that has been neck turned will crack, sometimes when seating bullets. The cracks themselves seem to show a radial force, what are the fired neck diameter vs loaded diameter?

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#3278589 - 06/23/21 09:08 PM Re: Question on why my 243 necks are cracking [Re: Dultimatpredator]
Frankm Offline
Seasoned Member

Registered: 10/25/19
Posts: 144
Loc: Idaho
+1
with Wyobull Ö. Generous chamber. Mic a loaded, unfired round and then Mic a fired round before sizing. See how much your necks are expanding. Much more than .006-.007 and that brass is getting worked hard. A tight neck bolt action as a comparison often only has .002 or so.

Do similar checks on the should diameter and the case diameter just below the web.

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#3278665 - 06/26/21 09:28 AM Re: Question on why my 243 necks are cracking [Re: Dultimatpredator]
IdahoSawtooth Offline
Seasoned Member

Registered: 01/07/07
Posts: 288
Loc: Idaho
Annealing will help. Every couple shots worked for my 220 swift.

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#3278756 - 06/29/21 06:02 AM Re: Question on why my 243 necks are cracking [Re: Dultimatpredator]
Dultimatpredator Offline
Die Hard Member III

Registered: 07/06/07
Posts: 2657
Loc: Wisconsin
Iím going to load some up with my regular size RCBS green box sizing die set and accuracy test to see it it tightens groups. I know the SB black box set opened up groups in my other 243 upper. Iíll have to see if the The regular sizer isnít as hard on brass. I did find out I trimmed my brass a little to short. It was a 2.020Ē. Donít know if trimming to short would have affected anything. I do know when I trimmed brass to 2.035Ē in my tightest grouping load combos it DID open up the groups. Must have been caused by more neck tension???

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