Split necks when fire forming

[Hengehold]

I am fire forming some 240 tomahawk brass (think 6mm SPC w/ 40deg shoulder) and am getting split necks in 10% or more of my cases. Is this a symptom of pressure problems (too low or too high)?

FYI, In hind sight I am using powder that is a little too slow for my application so possible that my pressure is a little low.

I also used some previously fire formed brass from another barrel in this new barrel and am now seeing splitting necks in 100% of cases. This is with a load that has powder with an appropriate burn rate.

-Trevor

 

[HandgunHTR]

Are you annealing at all? Necking the brass down will work harden it. Especially if this is in a gas gun where the case necks get beat up a bit due to impacts with the brass deflector or the ground.

 

[acloco]

Build a dummy round, blacken the neck AND shoulder area, allow to dry, chamber the round, and post a picture please.

 

[Hengehold]

Are you annealing at all? Necking the brass down will work harden it. Especially if this is in a gas gun where the case necks get beat up a bit due to impacts with the brass deflector or the ground.

No, not annealing at this time.

Necked down from 6.8mm to 6mm.

Fire forming with a false shoulder on the neck from necking down.

 

[Turpentine]

My first thought also as mentioned went to annealing. It sure couldn't hurt

 

[Hengehold]

My first thought also as mentioned went to annealing. It sure couldn't hurt

My plan was to try and have the cases annealed after the first firing. Apparently it may be more beneficial to do it prior to the first firing after necking down.

 

[DJSBRS]

I recommend annealing prior to and after sizing down your cases and depending on how much your moving the brass around, anneal during the midway process.

DJ
DJ's Brass Service

 

[Turpentine]

With my 65-06 I anneal once fired 30-06 cases, then neck down to 6.5-06. Then I'll anneal after each firing before re sizing. Call me crazy but I hand anneal and kind of enjoy the process. The brass seems to size much more consistently when I anneal.

 

[Ray123]

I sized 25-06 from 30-06, in 1972 no annealing no problem with necks, 6.5 Grendel to 6 ARC 1200 pcs no annealing, 358 W from 308 W, no annealing, 350 Rem mag from all belted mags 7 mm to 300 H&H no annesling no problem. no problem 35 Rem from 308 W no annealing, 8.6 Blackout from 30-06,270, 25-06 308 300 Savage, no annealing no problem with necks. Infact annealing here caused problems with forming.
But 6.5 Grendel basic .430 straight wall to 6 mm ARC required 4 annealings per case to get it down to 6mm...it says to anneal on Starline's website when using this case for wildcats cause it's left hard, to anneal before sizing ...I tried one...it cracked full length on the 1st try to test their instructions... so I annealed the 249 pcs left, no problem. So here annealing was necessary as the case was left hard at Starline. Most of the rest of serious case forming does not require annealing, also it's part of die making I make many of my own dies especially roughing out wildcats.
So, no annealing, I'm capable of moving a 270 W .650" down with 30° shoulder in one pass no lube is even necessary, they even get warm from friction with no lube....but I usually spray very lightly with Hornady spray lube to form the perfect 30° shoulder for the short cased 8.6 Blackout, 300 gr 3 twist AR 10 cartridge. But ya have serious neck turning to do, no problem on a lathe.
So I never anneal unless it's necessary, as you can see, it's mostly not necessary. I have never annealed a single pistol case in the many thousands I have fired...so why should I be obsessed with it for rifle cases, as many seem to be . I am not, and I form alot of different cases. Not even my 6 dasher has seen an annealed neck!
And most likely, it never will. Id rather be shooting. But if you like the process keep on doin it, it aint my time, ain't my case.
But it's possible to move alot of brass without any annealing, some of the secret is the die, you make...but since most are not machinist the knowledge won't do ya any good ...so you're stuck with what the manufacturers give you. You want improvement, learn, experiment, and do it for yourself,..invent, use your own ideas,... then, use what works for you.

 

[Webster]

Are you annealing at all? Necking the brass down will work harden it. Especially if this is in a gas gun where the case necks get beat up a bit due to impacts with the brass deflector or the ground.

Gas guns should have a bigger chamber than bolt action. This means your moving the brass more when sizing. Annealing each time should solve the problem. Splitting can only occur from work hardening.

 

[Turpentine]

I sized 25-06 from 30-06, in 1972 no annealing no problem with necks, 6.5 Grendel to 6 ARC 1200 pcs no annealing, 358 W from 308 W, no annealing, 350 Rem mag from all belted mags 7 mm to 300 H&H no annesling no problem. no problem 35 Rem from 308 W no annealing, 8.6 Blackout from 30-06,270, 25-06 308 300 Savage, no annealing no problem with necks. Infact annealing here caused problems with forming.
But 6.5 Grendel basic .430 straight wall to 6 mm ARC required 4 annealings per case to get it down to 6mm...it says to anneal on Starline's website when using this case for wildcats cause it's left hard, to anneal before sizing ...I tried one...it cracked full length on the 1st try to test their instructions... so I annealed the 249 pcs left, no problem. So here annealing was necessary as the case was left hard at Starline. Most of the rest of serious case forming does not require annealing, also it's part of die making I make many of my own dies especially roughing out wildcats.
So, no annealing, I'm capable of moving a 270 W .650" down with 30° shoulder in one pass no lube is even necessary, they even get warm from friction with no lube....but I usually spray very lightly with Hornady spray lube to form the perfect 30° shoulder for the short cased 8.6 Blackout, 300 gr 3 twist AR 10 cartridge. But ya have serious neck turning to do, no problem on a lathe.
So I never anneal unless it's necessary, as you can see, it's mostly not necessary. I have never annealed a single pistol case in the many thousands I have fired...so why should I be obsessed with it for rifle cases, as many seem to be . I am not, and I form alot of different cases. Not even my 6 dasher has seen an annealed neck!
And most likely, it never will. Id rather be shooting. But if you like the process keep on doin it, it aint my time, ain't my case.
But it's possible to move alot of brass without any annealing, some of the secret is the die, you make...but since most are not machinist the knowledge won't do ya any good ...so you're stuck with what the manufacturers give you. You want improvement, learn, experiment, and do it for yourself,..invent, use your own ideas,... then, use what works for you.

I've had no issues to speak of when not annealing With the 6.5-06. But my brass seems to size softer and more consistently when I do. It does help me get more milage from my 6.5 Grendel brass as one of mine is a brass stretcher. I have a new bolt that will fix that. But like I said I like to anneal anyway.

 

[MikeRu]

Agree with above annealing comments, and might help some to use a hard jam and higher neck tension such as 0.002-0.003 or so.

 

[Hengehold]

Agree with above annealing comments, and might help some to use a hard jam and higher neck tension such as 0.002-0.003 or so.

Why do you recommend this?

Is it to increase the chamber pressure?

 

[Webster]

I've had no issues to speak of when not annealing With the 6.5-06. But my brass seems to size softer and more consistently when I do. It does help me get more milage from my 6.5 Grendel brass as one of mine is a brass stretcher. I have a new bolt that will fix that. But like I said I like to anneal anyway.

What does the bolt have to do with brass stretching?

 

[Turpentine]

My old bolt face was cut a bit too deep. my chamber is in spec but slightly on the long side. It creates a headspace issue. My brass from that gun winds up .006- .007 longer headspace than my other Grendel's I load for. I have to separate brass for each and make sure I don't mix my loaded ammo. This gun is very tough on brass and I may end up swapping barrel out also. It's finicky accuracy wise but shoots great with the right loads. But it will digest about everything you want to put in it. Kind of AKish.

 

[Mark W]

Why do you recommend this?

Is it to increase the chamber pressure?

It’s done to hold the case head against the bolt face, so the brass movement will occur at the shoulder.

 

[Hengehold]

It’s done to hold the case head against the bolt face, so the brass movement will occur at the shoulder.

Understood. However, I am already doing this with a false shoulder when I reduce the neck diameter so I believe that it is probably a moot point.

 

[Webster]

My old bolt face was cut a bit too deep. my chamber is in spec but slightly on the long side. It creates a headspace issue. My brass from that gun winds up .006- .007 longer headspace than my other Grendel's I load for. I have to separate brass for each and make sure I don't mix my loaded ammo. This gun is very tough on brass and I may end up swapping barrel out also. It's finicky accuracy wise but shoots great with the right loads. But it will digest about everything you want to put in it. Kind of AKish.

Not sure what you mean by the chamber is to long requiring a new bolt. You said it's in spec. SAAMI specs are not important. As long as you can FL size the case and bump the shoulder 2 thou I would leave it alone. Just shoot it. A barrel and a bolt are expensive just to create a situation that you can use the same brass in 2 rifles.

 

[Turpentine]

The chamber isn't too long. It's in spec but on the long side of spec. The bolt face is just a shade deep so I get tolerance stack. It's the first AR I ever built. Years ago. Plus it shoots absolutely terrible with factory headspaced loads. The 20" 1 in 8 Wilson arms barrel also doesn't care much for 123's. It likes 129, 130s. I have an extra bolt from a few builds ago as I build a bunch of ARs. I've accrued a lot of parts over the years. So the cost of trying a different bolt is zero. Plus I have wanted to reconfigure that rig anyway. Not a case of having to do anything. Simply wanting to do something different.

 

[1shot]

I recommend annealing prior to and after sizing down your cases and depending on how much your moving the brass around, anneal during the midway process.

DJ
DJ's Brass Service

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