Neck Cracks

[TNBilly]

Just noticed this on a couple fired rounds....

This is 25/06 made from 30/06 brass. No neck turning and it was before I knew the value of annealing necks as well. The loaded rounds measure at the neck (.287) before firing, (.291) after firing. Regular 25/06 brass measures generally /257-8 before firing. My question is whether the location of the cracking signifies a too tight neck or is more of a coincident of a hard neck? Most neck cracking I've run across runs from the mouth of the neck inward and I account to either hard or wore-out brass. Anyone see a significance of the cracks location here? What should I consider a minimum neck clearance? I realize it's closer than "standard" but what's too close?

 

[rg1]

Looks more like a defect from the original manufacture? Doesn't look like a crack but a fold caused when the case was formed. Sometimes on military brass especially too much material will cause the brass to fold in at the neck shoulder area. Look inside the neck and see if there is material folded in. I wouldn't reload that case again. Maybe it's a crack but could be a fold. Higher zoom does look like a crack?

 

[TNBilly]

most definitely a crack, but you bring up a good point I might have caused it when I formed the brass. I have some more I formed but haven't loaded as yet, I'll look them over closer!

 

[popper]

Fast powder with a light bullet? I got that all the time with the base not fully into the neck in 30/30. the neck takes full pressure (large throat?) and you get a 'burn out' at any weak spot. Annealing may help, not annealing before forming may have weakened the neck. Worn out brass usually splits at the mouth.

 

[Hondo 60]

Annealing may help, not annealing before forming may have weakened the neck.

Seems like that right there is your key.
The case shown doesn't seem to be annealled.
Not that you NEED to anneal all of them, but if it's cracking with a low reload count, that's where I'd start.
(or if you have a lot of brass, just scrap it & load with the others)

 

[Fire_Moose]

Isn't a cracked shoulder a sign if excessive headspace?

Sent from my CZ85 Combat

 

[ZeSpectre]

I was thinking a headspace problem too but I'm certainly no expert there.

 

[243winxb]

30-06 to 25-06

The neck cracks because its unsupported. The neck/shoulder junction is .076" difference on the SAAMI drawings. Length, head to junction. This means the shoulder of the 30-06 must blow forward that amount? Annealing before may help. But the shoulder, if to soft may bulge/collapse. Setting a false shoulder to get good headspace may help. Loaded round clearance in the neck/chamber area, needs to be .003" minimum. I have see Fuji factory ammo in 30-06 do the same thing on firing. A donut may form at the neck shoulder junction, be carefull of this. When bullets are seated into the donut, the rounds may chamber hard, pinching the bullet in the case.

 

[Tolkachi Robotnik]

Working it that much ages and hardens.

I've made .270 cartridge cases into 25-06. They too would fail in the necks in fairly short order. Part of this is due to fatigue on the heavily worked brittle necks. Any fast powder with lighter bullets will result in this failure faster. I only shoot three or four times before retiring brass that has .270 headstamps. It is also hard because they come out long and need a lot of trimming. There are less problems with the right brass, and it is less work.

The necks might last a little longer if you turn them down on a lathe to reduce the thickness of the neck, until they are within proper tolerances. Remind yourself that this is also a reworking and a hardening for the brass. Annealing might help a little but you are putting the brass through a lot of reshape work.

I would not consider it a shoulder failure, it is more due the fatigue on the reworked necks.

For the most part reloading a rimless cartridge you are not likely pushing the shoulder back much from the chamber of your rifle. You are reworking the necks a lot more.

If even one or two of a set of fired cartridges does this type of neck failure you need to retire the entire set and start with something new and fresher. They are getting thick in the necks, and will likely fail worse the next time even if they show nothing visible. A micrometer would likely show they are thick. Even if you squeeze them down to proper outer diameter, the inside is thick and the bullets are held too well, increasing pressure. As the bullet leaves the extra pressure is trying to leave and ends up splitting the necks.

 

[cfullgraf]

This is 25/06 made from 30/06 brass. No neck turning and it was before I knew the value of annealing necks as well.

i have seen the same kind of cracks when reforming 308 Win to 6.5x54 Kurz Mauser.

I do not see the cracks when using 7x57 or 7mm08 cases so, in part, so I suspect the big step in reducing the case neck is part of the problem.

Annealing may help but it sounds like Tolkachi Robotnik has some good suggestions as well.

 

[lightman]

I'm guessing that that crack is from being work hardened. Everybodys QC seems to have slipped some since the shortages of 2008. I have had new cases get neck splits on the 2nd firing, lately. I finally bought an annealing machine. Cases are pretty cheap, but I put a lot of prep into mine, and hate to loose them so soon. Lightman

 

[TNBilly]

I'm leaning towards it being work hardening. The failure is right in front of the area that is the new neck formed so probably is worked the hardest. I annealed a batch tonight I was getting ready to load, I'm wanting to work up some of the new 117's, so I'll see within a couple loadings if there's a difference.

I didn't state it but as it got brought up these were not light bullet or quick powder loads. All 414 or 4831 with 100 or heaver bullets. Most of my accuracy loads tend to be max or really close to it as well.

243.... the shoulder on the 2506 is the same distance off the base and the same angle as the 30-06 so there's no "shoulder lacking" for fire forming. There's only, sometimes a small amount of the angle from the shoulder to the neck that doesn't form as distinctly as it should. It does form out on the first firing though.

 

[243winxb]

Check SAAMI drawings, see where both neck/shoulder junctions are measured at. Looks like 2.185" & 2.109" to me. Just a guess on my part. http://www.saami.org/specifications_and_information/index.cfm?page=CC The maximum neck diameter of a loaded round on SAAMI looks like .291" at the junction. I will admit, i dont understand how both can have the same shoulder angle, but have the junction at different distances from the case head. Plus the body from the head to the start of the shoulder is the same. 1.948" Some one explain it to me. 25-06 http://www.saami.org/PubResources/CC_Drawings/Rifle/25-06%20Remington.pdf and 30-06> http://www.saami.org/PubResources/CC_Drawings/Rifle/30-06%20Springfield.pdf

 

[TNBilly]

Check SAAMI drawings, see where both neck/shoulder junctions are measured at. Looks like 2.185" & 2.109" to me. Just a guess on my part. http://www.saami.org/specifications_and_information/index.cfm?page=CC The maximum neck diameter of a loaded round on SAAMI looks like .291" at the junction. I will admit, i dont understand how both can have the same shoulder angle, but have the junction at different distances from the case head. Plus the body from the head to the start of the shoulder is the same. 1.948" Some one explain it to me. 25-06 http://www.saami.org/PubResources/CC_Drawings/Rifle/25-06%20Remington.pdf and 30-06> http://www.saami.org/PubResources/CC_Drawings/Rifle/30-06%20Springfield.pdf

The junction of the neck to the shoulder is at a different diameter! Of course there will be a difference of THAT location as measured from the base. Where the shoulder starts is the 1.94~ dimension off the base is the same and tapers to the neck diameter from there.

 

[ranger335v]

What we can know about neck cracks anywhere is that there is either a hard or thin place where the crack forms; it's no more complex than that. Hardening comes from excessive working and that's what annealing is all about.

 

[243winxb]

Ok, i get it.