Cracked Casings - Please help!!!

[Orcon]

I used the term "excessive headspace conditions" in the same manner as Walkalong's "artificial headspace". For most reloaders the term only relevant to the relationship of a sized case and the chamber. I reload for a rifle that I can close a no-go gauge on. No big deal, I simply size my brass down .003" under what a fired case is. Technically speaking this rifle has "excessive headspace" but after initial firing I remove the excessive headspace conditions by sizing accordingly.

 

[Walkalong]

Technically speaking this rifle has "excessive headspace" but after initial firing I remove the excessive headspace conditions by sizing accordingly.

Exactly, fitting the brass to the chamber, eliminating excess head clearance, making it safe to fire.

.303 British shooters do this all the time.

 

[Blue68f100]

Since you don't have gauges you can do it the old fashion way. Find a straight wall pistol brass ( 9mm, 380 should work) that slips over the neck and contacts the shoulder. Use this to measure from base to base, then compare the number to your sized brass. This will give you a difference if your moving the shoulder back. It's the poor mans way of doing with what you have to work with.

 

[Orcon]

Since you don't have gauges you can do it the old fashion way. Find a straight wall pistol brass ( 9mm, 380 should work) that slips over the neck and contacts the shoulder. Use this to measure from base to base, then compare the number to your sized brass. This will give you a difference if your moving the shoulder back. It's the poor mans way of doing with what you have to work with.

Simpler yet, take that die and back it out 2 turns. Grab the rifle in question and work the bolt a few times on an empty chamber, make a mental note on how closure feels. Take an unsized fired case, chamber it and close bolt a few times and make a mental note on how closure feels. There should be a noticeable difference between the two. Lube the fired case, run it through the sizing die. Chamber the case and close the bolt. Still stiff? Turn the sizing die down a quarter turn and run the case through the sizing die. Chamber the case and close the bolt. Still stiff? Repeat these steps until the bolt closes with the slightest resistance and give it an additional 1/8th turn and lock the die. Pat yourself on the back for properly setting up your sizing die.

 

[IMtheNRA]

Fellas, I agree that excessive resizing would cause this failure, but I have a couple of questions.

1. What explains the extra loud shot and rifle jump that the OP reported.

2. How can the Lee collet neck sizer set the shoulders back? I was under the impression that the OP uses this die.

 

[redbullitt]

I'm with Orcon. I would size the cases so they JUST fit in the chamber. See how far away that is from where you were screwing the die to. You may need to get another sizing die to do this, but you will need one sooner or later anyways. Cant neck size forever, so may as well kill 2 birds with one stone.

Would like to add another thought. The history of the brass may be part or all of the issue. Maybe it was stretched out and overworked before you ever got ahold of it. Perhaps fired in a belt fed or something with a generous chamber. I have encountered quite a few pieces of 308 like this, especially in mixed once fired batches.

 

[edwardware]

1. What explains the extra loud shot and rifle jump that the OP reported.

The surprise of having a small bit of ~65kpsi chamber pressure vented in close proximity to your nose can create the impression it was louder and recoiled harder. I've experienced that as a consequence of excessive cartridge headspace caused by oversizing brass.

2. How can the Lee collet neck sizer set the shoulders back? I was under the impression that the OP uses this die.

It can't. If the Lee Collet Neck Size die is the only operation used, then something else is going on; that die can not move the shoulder.

I agree with many of the above posters: get one of the many gauges to measure shoulder position, and measure it. Measure factory new, once fired, sized, twice fired, etc. I bet the issue will jump right out at you once you have adequate measurement tools.

 

[rjs5244]

I will check the shoulder lengths this morning and report what I find. I called Lee and talked to their engineers and they assured me that the Lee Collet Neck Sizing die cannot adjust the shoulder. After speaking with them I disassembled the die and examined it. As a mechanical engineer myself, I would have to agree that the die is designed to only push the neck inward and it would not move the neck up or down. All the brass was purchased within the last 4 years, the brass is mixed lots but they are all from core lokt ammo and only fired once and from my rifle. I was under the impression that these casings should be perfectly formed to fit my rifle and all that would be required to do was to neck size for the most accurate round.

I spoke with a buddy last night who suggested that that I am seating my bullet too far off the rifling. Currently, the I am loading to an OAL of 3.320". I half seated a bullet into a sized casing, chambered that round so that the rifling would finish seating the bullet, and measured the length of that round to be 3.472". He measured the distance to rifling a different way and came up with 3.465" (very similar). That means that these rounds have to jump nearly 0.150" before reaching the rifling. He is convinced that this is my problem and to start seating the rounds at 3.450". Any thoughts on this? I am nervous to seat the bullets so much further forward than what is recommended in the books

 

[243winxb]

Your buddy is wrong on the OAL. 3.320" is listed at Nosler. https://load-data.nosler.com/load-data/30-06-springfield/

If sizing is not excessive, your looking at defective brass.

This album has some photos like yours. https://www.thehighroad.org/index.php?media/albums/kaboom.24/

Some new brass is formed by swaging a case head on to an extruded case body. If not done correctly, KABOOM.

 

[243winxb]

Note the raised mark from the ejector hole on this Remington 270 brass. The mark can be seen on some factory ammo. Normal, unless its raised a lot that a thumb nail catches on it.

I dont see the mark on your brass? Your loading is light. Light loads do not expand brass fully to the chamber. The head to datum measurement may even get shorter.

 

[rjs5244]

Attached are some shoulder measurements using a 9mm casing slipped over the neck of the 30-06 brass. After measuring I subtracted the length of the 9mm brass. Keep in mind that the 9mm casing most likely did not rest on the exact part of the shoulder where the measurement should be taken from. It looks to me that the shoulders are in fact being pushed back around .009"

 

[Walkalong]

It looks to me that the shoulders are in fact being pushed back around .009"

Assuming good measurements, that is enough to do it.

 

[Walkalong]

Oh, and you do not have to subtract the 9MM case, simply get the difference.

 

[Walkalong]

Using my little home made "gauge" I get a number on fired brass, then a number on sized brass, the only number that means anything is the difference between the two.

 

[243winxb]

2.094"
- 2.075"
--------------
.019" Difference between maximum and minimum. Case separation for sure.

No factory ammo measurement?

Looks like the collet neck sizer is pushing the shoulder back? Or changing the shoulder angle?

 

[Walkalong]

If you set the caliper to zero on the fired brass, then when you measure the sized brass you will get the amount it is moved, but I just do the math. Average 2.202 on fired? I need an average 2.200 on sized. Or whatever amount you want to move the shoulder, but I wouldn't go over .003 with a bolt gun.

 

[Leatherstocking]

I am neck sizing using the Lee ultimate die set.

Did the OP full length size AND neck size. I believe this die set includes both dies. I agree with most who say setting the shoulder back too much would cause the case head separation.
Which die from the set did he use?

 

[Tony k]

Did the OP full length size AND neck size. I believe this die set includes both dies. I agree with most who say setting the shoulder back too much would cause the case head separation.
Which die from the set did he use?

Is it possible for the collet sizer to interfere with the shoulder? I've been looking at this cut away on the cover of the Lee manual.

assuming the clearances between the mock up and OPs actual die, I think it's possible to adjust the die body too far down, thus hitting the shoulder. I Know Im reaching. We still need clarification on OPs sizing procedure. but I just got a Lee collet sizer and I want to learn from this event rather than creating my own.

 

[rjs5244]

This is the lee collet neck sizer. The shell holder pushes up on the slotted sleeve that is guided by the die body. The sleeve then contacts the short tapered cylinder that compress the slots on the sleeve and compresses the neck of the brass. That compression is stopped when the inside of the neck of the brass contacts the mandrel (the mandrel also deprimes the brass). There are no adjustments on the actual sizing process. The die needs to be turned a minimum of 1 full turn after contacting the shell holder. The die can be turned in further than the 1 full turn with no effect on how this die will size. I confirmed this information with the engineers at lee precision.

 

[Leatherstocking]

RJS, did you only neck size, or did you full length size as well? Probably a dumb question.

 

[rjs5244]

I only have neck sized because it provides a more accurate round and it is my goal to someday shoot up to 1000 yards. I will try full sizing but I don't want to shoot any more with this gun until I feel confident the issue is found. I cut open some casing length wise and they're in the tumbler now. I will post the pictures when they are cleaned up.

 

[rfwobbly]

I spoke with a buddy last night who suggested that that I am seating my bullet too far off the rifling. [snip] That means that these rounds have to jump nearly 0.150" before reaching the rifling. He is convinced that this is my problem and to start seating the rounds at 3.450". Any thoughts on this? I am nervous to seat the bullets so much further forward than what is recommended in the books.

Your friend means well, but is mistaken. While there is a "Minimum Jump to Rifling", there is no "Max JTR" which causes the safety hazards you are experiencing. Yes, you may experience some very minor loss of bullet accuracy, but your safety is the over-riding concern here.

Your bullet manufacturer knows how much seating depth the bullet requires into the case to achieve the best results. There is a Max OAL for each cartridge, which mainly has to deal with the finished cartridges fitting into the magazine. As bullets get lighter (and therefore shorter), in order to maintain the minimum bullet-to-case neck engagement, the OAL has to grow shorter. Your bullet makers knows this and has already calculated a slightly shorter OAL for each successively lighter (shorter) bullet. So, you'd do well to follow the bullet maker's recommendations.

All the best.

 

[243winxb]

Forget the collet die.

Set up the full length die with a gap of .010" between the shell holder and bottom of the die. Use a feeler gauge. Size 3 brass, does brass let the bolt close? Measure shoulder set back or movement forward. FYI - FL sizing may move the shoulder forward.

The only time i seen this much difference in shoulder bump, was with a defective Dillon Shell Plate. It was different at each station.

 

[Walkalong]

The slotted crimp sleeve could be too short and the "shoulder" area of it could be hitting the shoulder of the brass.

 

[Nature Boy]

I have one of those lee collet neck sizers and tried it with .308. It did move the shoulder back on my brass.

How do I know? I have a comparator that allows me to measure it.

Get a Hornady headspace comparator so you know what you are doing to your brass.

I don’t use the lee neck sizer anymore. I found inconsistency in neck tension and degradation in accuracy.

So I echo what others have told you. After you have a method for empirically measuring your shoulder set back, get a full length sizing die