Brass "indent" issue...what causes this?

[GAnderson]

dkhunt, I agree...I just looked a little bit ago and the date printed on the Alliant load data sheets I have are from 2005...a lot can change in that many years. I had gone away from 10X in favor of AA2520, but ran out of that and haven't seen any for sale in almost 2 years now...this is why I broke open the Jug of 10X a year or so ago. I may have to burn the 10x up in something else. Thanks

Gene

 

[fguffey]

Every once in a while I get a fired piece of brass that comes out like this...

I do not nave fired cases with collapsed shoulder/case bodies; I find nothing entertaining about reduce loads. Then there is that balancing thing when using slow powder, I have ejected cases with soot on the necks; at times it is difficult to remove.


The case pictured did not seal the chamber when fired. When pressure inside the case does not seal the chamber gas is trapped between the case body and chamber. When the pressure inside the case drops the gas trapped between the case body and chamber collapses the case from the outside in. There are times the pressure rips the case like it was hit with a shaped charge.


F. Guffey

 

[effendude]

Along with the other excellent answers referring to a low pressure charge not sealing the neck, it may simply be your reloading methods. Are you charging directly from, the powder measure into each case? It wouldn't take much of a short/under charge to cause this with a small charge to begin with

Scott

 

[GAnderson]

effendude, good thought...but I use an RCBS chargemaster combo for all of my loads and don't use a powder thrower. Yes, I calibrate the chargemaster frequently and verify weights with another scale periodically.

Based on some responses I want to be very clear that I am not intentionally "playing" or getting "entertained" with reduced loads at all. I personally don't see the logic in reduced loads. I have been loading to previously published load data from Alliant for this powder at the max charge listed...reference post #7...I don't know what else to say other than I had been following the manufacturer's published data for years without issue...this just started with a new jug of powder.
I do think however, based upon most of the responses, that this new lot of powder may NOW be putting this previously published max load into a marginally slow and/or reduced load category. Alliant did make some changes to "clean" up this powder and this is the first of this "new and improved" powder that I have tried...so far, this is the only variable. Having never experienced ever before this type of issue with any brass/caliber after firing, I thought I would inquire as to what the cause or causes could be. I did receive some relevant information in a PM from a person that sent a link to another forum where similar issues were happening with this powder and that the "fix" was a significant increase in the charge weight and in some cases, the use of magnum primers. Apparently enough changes were made to the powder that resulted in a reduced density and burn rate(as Donovan eluded to)...AND as one person responded, "there is probably a good reason that they don't publish data for this powder and the 204 anymore". So now that I have tapped into this new jug of powder, what was working for me with the old batches of powder for so many years is definitely not working now...it has just cropped up with this new jug of powder. I think we are all for the most part in agreement on the cause/causes...it just threw me...after 10+ years of the same load, same everything...it just all of a sudden started having this problem "randomly" occur. I am very particular with my loading and it bothers me when something starts happening just "out of the blue"...no matter how isolated or random it may be. It really was a very reliable and consistently accurate load for many years without any problems. I may try upping the charge and possibly magnum primers but it may just be time to move on to 8208 or wait on AA2520(whenever it gets back on the shelves). Thanks again to all for the responses...a lot of good information has been put out there.

Gene

 

[Shaggy357]

...this just started with a new jug of powder.
I do think however, based upon most of the responses, that this new lot of powder may NOW be putting this previously published max load into a marginally slow and/or reduced load category.

Gene

Gene I agree with this remark. I have found this to occur in a couple of my reloads using a powder on the "slow" end of the scale. Most often, the brass was on firing 4 or more without having been annealed again. Neck gets a little work hardened and does not expand as fast as shoulder and gas escapes. As slower powder reaches peak pressure gas is trapped in generous chamber space and dent results. Annealed several batches of brass when this occurred. Also went to a faster powder in several of my old military war horses due to this.

 

[Brians356]

Light neck tension on some, with a result of secondary pressure spike from the bullet moving to soon. The neck did not seal, pressure higher on the outside than inside. Use a faster powder or a magnum primer. http://thefiringline.com/forums/showthread.php?p=4928827#post4928827

As I envision it (having read nothing about the phenomenon, or experienced it myself) the only way this could happen would be:

1. Pressure builds and enough expanding gas escapes the case before the neck expands and seals off the chamber.
2. The neck finally seals, trapping the escaped gas outside the case but within the chamber.
3. The trapped gas continues to expand enough to form the indentation.

It would seem more likely to occur if the case had been fired in the chamber at least once, allowing the expansion ring near the base to expand to the chamber diameter. A tight enough fit there (even after minimal body resizing) would allow the escaped gas to be trapped around the forward part of the body after the neck expanded and sealed.

 

[Brians356]

Gene I agree with this remark. I have found this to occur in a couple of my reloads using a powder on the "slow" end of the scale. Most often, the brass was on firing 4 or more without having been annealed again. Neck gets a little work hardened and does not expand as fast as shoulder and gas escapes. As slower powder reaches peak pressure gas is trapped in generous chamber space and dent results. Annealed several batches of brass when this occurred. Also went to a faster powder in several of my old military war horses due to this.

Some powders which one would assume suitable for a particular cartridge simply aren't. A perfect example:

Hodgdon publishes CFE 223 load data for 243 Win and 243 WSSM, but not for 6mm Rem. Figuring they simply hadn't yet gotten around to developing data for 6mm Rem, I called Hodgdon and asked when they planned to publish it. "Never" was the response. "We found CFE 223 to be too unstable in 6mm Rem. Do not use it in that cartridge." Huh.

Curious about that, I looked closely at existing data for those three 6mm cartridges, and while there are obvious and distinct differences between 243 Win and 6mm Rem (their data are far from similar) I was surprised to discover that 243 WSSM is very close to 6mm Rem WRT internal ballistics (closer than any other two disparate cartridges you can name) yet CFE 223 is suitable only for the former. Go figure.

So it seems reasonable to me that even a subtle change to 10x could have rendered it unsuitable for 204 Ruger, even if it had previously been excellent for it.

 

[dkhunt14]

As I envision it (having read nothing about the phenomenon, or experienced it myself) the only way this could happen would be:

1. Pressure builds and enough expanding gas escapes the case before the neck expands and seals off the chamber.
2. The neck finally seals, trapping the escaped gas outside the case but within the chamber.
3. The trapped gas continues to expand enough to form the indentation.

It would seem more likely to occur if the case had been fired in the chamber at least once, allowing the expansion ring near the base to expand to the chamber diameter. A tight enough fit there (even after minimal body resizing) would allow the escaped gas to be trapped around the forward part of the body after the neck expanded and sealed.

I have seen it happen fire forming a 340 Weatherby into a 308 Baer. These were full power loads with the load shot in matches. Bullets seated into the lands and no light loads or slow powder. Matt

 

[Brians356]

I have seen it happen fire forming a 340 Weatherby into a 308 Baer. These were full power loads with the load shot in matches. Bullets seated into the lands and no light loads or slow powder. Matt

It occurs to me that the bullet would come into play as well, as in the bullet is jammed into or close enough to the lands that it seals off the chamber before the neck expands completely. It's all in the split second timing, fleeting transient conditions have to be just right for the expanding gas to get trapped. The part I grasp the least is the powder load density vs burn rate part, and how that comes into play.

 

[dkhunt14]

It occurs to me that the bullet would come into play as well, as in the bullet is jammed into or close enough to the lands that it seals off the chamber before the neck expands completely. It's all in the split second timing, fleeting transient conditions have to be just right for the expanding gas to get trapped. The part I grasp the least is the powder load density vs burn rate part, and how that comes into play.

Shot the same combination in matches hundreds of times and so did others. Matt

 

[Brians356]

Shot the same combination in matches hundreds of times and so did others. Matt

Meaning ... what?

Shot the same combination as the OP "GAnderson"?

 

[dkhunt14]

Meaning what causes it, It is not the bullet in the lands, did it hundreds of times. Same lot of everything and same load. Not slow powder or reduced loads. Actually fireforming with the bullet in the lands was quite accurate. Won a lot of relays in 1000 yard BR doing it. Matt

 

[GAnderson]

So it seems reasonable to me that even a subtle change to 10x could have rendered it unsuitable for 204 Ruger, even if it had previously been excellent for it.

Brian, this seems to be the reasonable conclusion...as has been noted by several replies...while it worked great years back, it still must have been close to being borderline and with changes to the current or "newer" manufacturing of this powder, it has put it below the acceptable parameters now for this cartridge...thus the reason that Alliant does not currently support load data for it anymore in the 204. This seems to be a rapidly growing issue with other powders as well...people that were using certain powders in shotgun reloading for years are experiencing problems with current/newer runs of the same powder...and I am reading of it becoming apparent in certain pistol powders too. The days of the "good old fashioned tried and true" powder/loads are getting fewer and fewer with advances in modern propellant technology. Thanks to all...this has been a very informative discussion.

Gene

 

[Brians356]

Meaning what causes it, It is not the bullet in the lands, did it hundreds of times. Same lot of everything and same load. Not slow powder or reduced loads. Actually fireforming with the bullet in the lands was quite accurate. Won a lot of relays in 1000 yard BR doing it. Matt

So you're saying you saw a collapsed case, with bullet in the lands, but you're sure that had nothing to do with it. Got it, thanks. (For the record, I never said bullet in lands would cause it, I said it could be a factor. I've shot thousands of bullets in the lands with nary a collapsed case.)

What did cause it in your case, then?