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

[GAnderson]

Every once in a while I get a fired piece of brass that comes out like this...it is in 204 and all loads are the same. Using 39gr bullets, Reloader 10X and CCI400 primers. I have used this combination for several years...it shoots really accurate but and just every once in a great while a fired brass will have this. Any thoughts on what is causing this? Thanks

 

[dmoran]

To low of load density, to fast of powder for the cartridge, or to light of charge.
The resultants are; peak pressure is happening to soon, and/or partially in the case.
Donovan

 

[ShootDots]

Every once in a while I get a fired piece of brass that comes out like this...it is in 204 and all loads are the same. Using 39gr bullets, Reloader 10X and CCI400 primers. I have used this combination for several years...it shoots really accurate but and just every once in a great while a fired brass will have this. Any thoughts on what is causing this? Thanks

What it actually looks like is a piece of SIZED brass that had too much lube on it when entering the sizing die. However, because you indicate that the brass comes out of the chamber AFTER just firing it, it would seem to me that there can be ONLY 1 reason. Somehow, at some point, gas is escaping around the neck and being forced back into the chamber area.

QUESTION: When you extract a piece of brass that has the dent, is there black soot on the case?

 

[GAnderson]

Donovan, I wondered about the load density...there is a fair amount of air space, but this has only happened about 4-5 times out of about a thousand rounds or more and I would have thought it would happen more often.
Shootdots, you are correct...this happens after firing the cartridge and is not a "lube dent"...there is some soot on the neck but not any soot past the neck. I almost think that the brass is getting "sucked" inward.
I usually don't know this has happened to the casing until I go to reload it again and see the dent...so I don't even know if it affected the group or not. I may shoot a couple of hundred rounds and it never happen and then once in a blue moon I will have one show up. I have used 10x for a number of years and it seems that this just showed up in the last couple of years...just wondering if the newest jug of powder has changed any. Thanks for the replies.

Gene

 

[dmoran]

Donovan, I wondered about the load density...there is a fair amount of air space, but this has only happened about 4-5 times out of about a thousand rounds or more and I would have thought it would happen more often.

When the load density is to low, the dent is caused and dependent on how the powder ends up laying in the case (from the excessive room) when chambered and fired. That creates a doubled combustion cycle when it does occur.
Donovan

 

[dmoran]

I have used 10x for a number of years and it seems that this just showed up in the last couple of years...just wondering if the newest jug of powder has changed any.

The new Lot of powder could have less "bulk density" and/or burn a little faster. Up the charge (safely) is my suggestion.
Donovan

 

[GAnderson]

I just went to alliant's load data site and they no longer list 10x for the 204...wonder if something has changed? I know the earlier years of this powder burned kind of dirty and supposedly they have "cleaned" it up. My notes have alliant's load charges back when it was listed for the 204 starting at 21.6/3200fps and going to 25.1/3700fps for a 39gr bullet...I have always used 25.0 and over my chrono it was 3796fps. I may try slowly "upping" the charge and see what it indicates. Thanks

Gene

 

[dmoran]

Gene -
If you still have some of your previous Lot of 10X, run it and the new Lot over a chronograph and see if there is difference.
Donovan

 

[GAnderson]

Donovan, unfortunately I don't have any of the old stuff...and this never showed up until I got into this 5# jug of 10X. I will however run this lot over the chrono and compare it to my old notes. Thanks

Gene

 

[Sheldon N]

However, because you indicate that the brass comes out of the chamber AFTER just firing it, it would seem to me that there can be ONLY 1 reason. Somehow, at some point, gas is escaping around the neck and being forced back into the chamber area.

+1

Somehow the neck of the cartridge is not sealing in the chamber on firing, and the escaping gas is causing the dent.

 

[savagedasher]

+1

Somehow the neck of the cartridge is not sealing in the chamber on firing, and the escaping gas is causing the dent.

I t is clearly a pressure dent . You said it was after you shot it . If their is no hole in the case . Your not pressuring the neck to seal. Low pressure can come from wrong or not enough powder. Without cron numbers all we can do is guess. Larry

 

[dkhunt14]

I've seen it caused by moisture in the chamber. May be a little cleaning fluid or oil. Matt

 

[WSM01]

Trim length ? Maybe too long. I've seen it happen but had more indents around the case .

 

[Paddyd]

Considering it is an inward dent, there is no noticeable soot on the case, it doesn't seem to me that it would have anything to do with either low charge or case mouth not expanding to seal the gases. Regardless of charge weight there (in my opinion) would be too much internal pressure to 'suck in ' a case wall. Looks more to me like something either was inside the sizer die and you never noticed it until you extracted the case ,which would seem to have to be a lowered charge as to not blow the case wall back out. Or you have something in the rifles chamber that is deforming it. Anyway, it's a mystery to me.

 

[Dusty Stevens]

Ive seen it from dudes trying to make subsonic loads. Donovan hit the nail on the head

 

[243winxb]

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

 

[GAnderson]

Case length is is -.010 off of max length, the cases are not dented previous to firing, 25.0 of 10X is not a subsonic load...it is at the max end of the spectrum. I know of several friends with 204's that struggled a little to get their 204 to shoot and after giving them this load it proved to be an excellent and accurate load...something has changed. I am thinking like Donovan said...this jug of powder is of a lesser density and may not be as fast as what I have used previously for years...I have been using this load combination for at least 5 years and just started to notice this issue coming from this 5# jug of powder...ironically, the accuracy has gone off some from what I used to get...thinking the "changes" to the powder have something to do with this...and given that Alliant doesn't list load data for the 204 with this powder anymore has me wondering too. When the weather straightens up a little, I will run some thru the chrono and see what is going on. It is very random when it happens, so the only thing that would show anything will be the chrono numbers. Thanks to all again.

Gene

 

[GAnderson]

243winxb...interesting read from the link you provided. I think the powder has been changed enough by Alliant that it is not as fast as it used to be and I could also be experiencing some fluctuations in neck tension. I have had a casing or two that the seating force seemed lighter than the rest...usually marked them to be thrown away after the next firing. I may have a combination of things but I honestly believe that the powder has somewhat been changed and that is the most prevalent issue. I have some magnum primers that I can try also. Just need the weather to cooperate now. Thanks

Gene

 

[dkhunt14]

Sometimes if a company stops listing a powder in there info, there is a reason they stop. Maybe they discover something or somebody else did. Matt

 

[Twoboxer]

. . . I think the powder has been changed enough by Alliant that it is not as fast as it used to be and . . .

While waiting for the weather to turn, might give them a call.