Deformed case from sizing die mystery

[CLT65]

Case head expansion, from serious over-pressure. A cartridge case is a precisely engineered thing; during manufacture the brass is worked repeatedly from a brass cup into what it becomes. The base is hard from the forming process, while the body and neck are annealed and soft.

The neck needs to be soft to expand and seal the gas, while the base needs to be hard to withstand the high pressure. The base is never supposed to expand, but it will if the pressure is way too high, or if somehow it got annealed, or was too soft from manufacture. I'm surprised that the primers pockets aren't loose.

I saw something very similar once, a long time ago. I had helped a friend get setup in reloading, but it was a year or two between the time I coached him through his first box, and the time he got around to loading more, and apparently he forgot the part about making sure the H4831 settles fully in the powder measure, and checking weights with his scale. Instead he just adjusted the measure to the max charge and only weighed the first couple throws, then went to town throwing directly from the measure into his .300 Win Mag cases, not realizing that as the powder settled, his cases were more and more over-charged. He contacted me wondering why his brass wouldn't resize.

 

[gmerkt]

It was as if the sizing die wiped brass down the case body as I moved it up into the sizing die.

I have a theory based on this, the over pressured cases bulged at the case head area. Sizing caught the extra metal and "wiped" it down.

I'm pretty sure what you've guessed above is what happened. Kinda like dough being rolled out on a breadboard. You didn't show us a before picture, but one such might've shown excessive expansion just ahead of the rim cut. Just for drill, you might check case length and find that these are just a taste longer than the ones that didn't over-expand. There is probably a narrowing (however slight at this point) of case material around the area where the die caused a ridge.

I've had this happen on 10mm Autos that had hot loads.

We used to see this happen on .45 ACP's sized on early carbide dies. In that matter, it wasn't over pressure but die design that caused the problem.

 

[Pepe-lepew]

I have a theory based on this, the over pressured cases bulged at the case head area. Sizing caught the extra metal and "wiped" it down.
I wish I would have measured the case body dia near the head to compare.

I think you have a good theory. It could also be caused by softer brass cases.

 

[DizzyJ]

What was the load recipe?

 

[Koda]

What was the load recipe?

The load recipe was actually a pressure ladder, to compare velocities from different powders to my established load. I tested HLVR and H335 for my 97gn Absolute Hammer bullet with A2520 to see if I could safely get more velocity than my A2520 recipe.
HLVR compared slower but safe in all.
H335 is a much faster burning powder. I creeped up on pressure in 1gn, .5gn, .3gn then .2gn increments. But a gas gun doesn't have bolt lift as an indicator and the first sign was just a faint swipe mark on the case head (30gn) and I wasn't certain if that was false cause I know the bolt rotates. The next shot at 31gn included an ejector mark... I should have stopped there, but I'm not used to the escalation in pressure signs with faster powders. With A2520 faint pressure signs can spread out over a full grain of charge weight (at least, in what Ive handloaded so far). My lesson learned is faster powders escalate pressure, faster.


Whats interesting and am still pondering is the results. HLVR is a usable alternative, good to know. H335 is a faster powder but burned out too soon... its safe upper limit was 100fps slower than my current A2520 recipe. My guess is a faster powder is better for a lighter bullet, in this caliber anyways and I think HLVR would be a possible choice for heavier bullets in this caliber (6.5 Grendel)

 

[Hemlock]

If it was a case of brass being "rolled down" wouldn't it show up as excess overall length after firing and before resizing?
I don't think any full-length resizing dies will size all the way down to the extractor groove.

 

[Koda]

If it was a case of brass being "rolled down" wouldn't it show up as excess overall length after firing and before resizing?
I don't think any full-length resizing dies will size all the way down to the extractor groove.

probably, I didnt measure the case length before sizing. After sizing the bad cases seem to be about .005-.007 longer. Agree FL dies dont size all the way down, mine probably stops where the ring showed up.

 

[Greg S]

If it was a first firing on the case it might have a manufacturing defect i.e. Ballon head. Had some Fiochi 45 acp like that. Weigh the case and compare to the others. If a discrepancy, weight the whole batch or lot. Could be more than one.

After the one case blew out I stopped. Went home and cleaned the brass (range pick up same boxes) and found 3 more Balloon headed cases in the 50-60 rounds I had shot.

If good on weight, insufficient lube a way over pressure. XBR?

 

[Koda]

If it was a first firing on the case it might have a manufacturing defect i.e. Ballon head. Had some Fiochi 45 acp like that. Weigh the case and compare to the others. If a discrepancy, weight the whole batch or lot. Could be more than one.

After the one case blew out I stopped. Went home and cleaned the brass (range pick up same boxes) and found 3 more Balloon headed cases in the 50-60 rounds I had shot.

If good on weight, insufficient lube a way over pressure. XBR?

Brass is Starline, these were their 3rd firing, Starline is good average brass. The non pressured cases held up fine. Im concluding this was my error reading pressure signs loading too hot.

 

[DizzyJ]

The load recipe was actually a pressure ladder, to compare velocities from different powders to my established load. I tested HLVR and H335 for my 97gn Absolute Hammer bullet with A2520 to see if I could safely get more velocity than my A2520 recipe.
HLVR compared slower but safe in all.
H335 is a much faster burning powder. I creeped up on pressure in 1gn, .5gn, .3gn then .2gn increments. But a gas gun doesn't have bolt lift as an indicator and the first sign was just a faint swipe mark on the case head (30gn) and I wasn't certain if that was false cause I know the bolt rotates. The next shot at 31gn included an ejector mark... I should have stopped there, but I'm not used to the escalation in pressure signs with faster powders. With A2520 faint pressure signs can spread out over a full grain of charge weight (at least, in what Ive handloaded so far). My lesson learned is faster powders escalate pressure, faster.


Whats interesting and am still pondering is the results. HLVR is a usable alternative, good to know. H335 is a faster powder but burned out too soon... its safe upper limit was 100fps slower than my current A2520 recipe. My guess is a faster powder is better for a lighter bullet, in this caliber anyways and I think HLVR would be a possible choice for heavier bullets in this caliber (6.5 Grendel)

Solid copper bullets?

 

[Koda]

Solid copper bullets?

Yes,

this is the bullet:

.264 Cal-097gr Absolute Hammer™ - Hammer Bullets

Based on the success of the 99gr Hammer Hunter, this 97gr Absolute Hammer™ will be a ton of really fast fun. A stiff dose of Ramshot Tac or rl-15 should get this one close to 3500 fps in the Creedmoor. The Absolute Hammer™s do not line up with conventional load data so only experienced...

hammerbullets.com

 

[DizzyJ]

Yes,

this is the bullet:

.264 Cal-097gr Absolute Hammer™ - Hammer Bullets

Based on the success of the 99gr Hammer Hunter, this 97gr Absolute Hammer™ will be a ton of really fast fun. A stiff dose of Ramshot Tac or rl-15 should get this one close to 3500 fps in the Creedmoor. The Absolute Hammer™s do not line up with conventional load data so only experienced...

hammerbullets.com

Maybe I missed it. How much jump?

 

[Koda]

Maybe I missed it. How much jump?

.075"

Note: Absolute Hammer bullets dont have an ogive that contacts the rifling. My dimension comes from the first drive band contact.

 

[DizzyJ]

After actually reading through the thread on my computer as opposed to my phone, I agree too much pressure. Was there actually load data for those powders and those particular bullets?

 

[Koda]

After actually reading through the thread on my computer as opposed to my phone, I agree too much pressure. Was there actually load data for those powders and those particular bullets?

Although Hammer has only very recently published load data for many of their bullets there is still no load data for this exact bullet. I establish safe starting points from other published data for similar weight bullets that listed my powders (typical Hammer practice).

 

[Hemlock]

Seams way back in my memory, when solids were becoming more common, it was recommended that they have more of a "jump" then the .010" us reloaders like to acquire.
It could be also that the chamber is a to touch long. This would allow extra case stretching. I have a 300 Savage that I have to leave an extra .010" long or all the brass comes out looking like it's over pressured.
Just some more thoughts.

 

[P7M13]

And i definitely pushed the pressure limit on this last test and should have stopped sooner but they were the last 5 rounds in the test.

Easy there, man!

 

[Caveman Jim]

I don't think it's supposed to do that.

Sometimes you just gotta stop and look at what you're doing, ya just gotta.