6Dasher Blowup

[roundknob]

OK Guys here we go.Im sure many of you have read about my stupity and blowing my dasher and almost myself up at a match this past weekend. My friend John Whidden at Whidden Gun Works which is about 25 minutes from here took the gun apart yesterday. John called me on the phone and told me he was putting my good parts in a plastic bag which included the jewl trigger and scope rail,everything else was trash except the stock. Along with extreme high pressure I am now questioning my reloading pratice. The dasher case was on its 8th firing and suffered from complete case head seperation. The firing pin was taken completly out along with the extractor,bolt release roll pins holding the extractor and bolt release all were broken out of the bolt and action. The first question I was asked was what was my headspace? I had fired 75 rounds that day and was down to my last five rounds in the last shootoff. I measured some of the remaining rounds last night with my stoney point gauge and was averaging about 1/2 to 1 thou.shoulder bump I also resized some more cases and came up with the same measurements.I also looked at all of the fired rounds and found signs of high pressure on the head ,but on about thirty of the cases right at the case head where the last one seperated is a ring protruding out enough your fingernail will hang on it.Any ideas?
Steve

 

[Hal]

Steve

I hope you were unharmed.

What powder were you using, and what temperature outside? Was the ammo in the sun?

Have you checked the neck diameters on your cases?

What do you use to weight your powder with?

Hal

 

[infantrytrophy]

Any chance you could post a picture of this ring you are seeing?

Two thoughts come to mind:
1 - Is the a portion of the case back near the case head that is unsupported by the chamber?
2 - The ring you describe could represent case stretching, maybe a cumulative effect due to several firing/resizing cycles. Check the remaining cases in this batch to see if there is a "stretch ring" on the outside or inside of the case wall.

Randy

 

[roundknob]

Randy
The portion is exactly where it is unsupported. I am going to try to post pics tomorrow and I am going to take my Dremal and cut a few open. The ring doesnt look like a stretch but rather like a rub ring.
Steve

 

[roundknob]

Hal
I replied but I see it did not post. I was running 33 grains of RL 15 temp was 85 degrees and they did see sunlight. The neck diameter loaded was .268 and fired was .271.
Steve

 

[mr45man]

Is it possible that the charge was a lot less than your normal load?
They say that a light load of powder will create a lot of pressure.

 

[lloydx2]

Are you annealing your cases? Case head getting to soft?

 

[roundknob]

I am annealing with a benchsource set on three.
Steve

 

[TheSnake]

Did John find anything he noticed or was he looking only for salvageable parts? I too would like to see pictures of the ruptured case, one of the cases with the protrusion and one without. This could be a learning experience for all of us and I am glad there is no long term harm to you.

 

[Frankr]

hope you are OK..thank god for the strong actions we have, P.o. ackley wrote some books on testing actions and trying to blow them up. very interesting reading..something like what i can remember is the brass case fails at 80,000 psi and most modern actions will fail at 165,000 psi..so usually you will stick a bolt jam it where the brass expanded beyond its ability to contract.. that's somewhere around 80,000 psi, if i remember correctly.
i shoot hot loads all the time but never where i have any bolt lift..one time i had a bunch of 22 ppc cases i was trying to save and followed a annealing process i read in a book and when i fired the first case it was bad..got some soot in the face and the primer hole was like twice the size, i did not shoot anymore and never tried any annealing since.. a local gunsmith sometimes has me shoot problem rifles for him..he had a 264 mag that would not shoot, sako action, custom stock etc..so he gave me some shells for it(factory) and i went to the range. i shot a few 3" groups and then the next shot i don't know what happend but it blew the back of case off , i have cat like reflexes and it took me off the bench and slamed me on the ground. just got like slight burn on my cheek and scared the sh** out of me..it gas cut the bolt face bad , bad enough it needed replaced. but no other damage. i don't know why it happened, the smith swears up and down they were factory shells..they looked factory.we think they were old shells that had sat in his shop and they were alittle tarnished maybe corroded enough to separate.don't know..but i still and allways run hot loads in everything i shoot and have never had a problem, i have allways seen the pressure signs..I shot in a match where i went up on the powder to get the tune and i could barley close the bolt on a fired case and they came out with the click at the top of the bolt lift.
but i will keep watching even closer now.. but i do have to wonder how much pressure was created to do the damage you stated and then how could a slightly hot load go that bad...??? I know one firend of mine his 300UM is set up for cold weather say 40 deg F and below and one day he took it ground hog hunting at 85+ deg F and he stuck his bolt we had to tap it open with a hammer..lol...

 

[Hal]

Steve

Is your loaded cartridges over all length still the same as when you loaded them?

How did you weigh you powder?

Hal

 

[roundknob]

Hal
I weigh my powder twice on a sartorious scale, once the powder goes in the hull and another time with the bullet in. I try to segregate my loads 1/2 grain increments before they go into the box. These loads were weighed twice. The fired lenghts are running from 1-3 thou.
Steve

 

[johara1]

I run 33.3 - .5 of RL-15 with the DTAC.115's with no problem and i was getting 30 loads out of the cases.I never had a head separate. I used that at 95 + degrees. I don't think it was the load but i did have a new case crack on the second load for no reason. Annealing even over annealed would not make the base soft unless you would have to almost melt the neck..... jim

 

[Keith Glasscock]

Had you sucessfully fired a round through the barrel since the last cleaning? I'm thinking that something had to be stuck in the barrel. Your load just wasn't hot enough to do that much damage without some "help."

 

[roundknob]

I was involved in an IBS match at 1000 yds. The shot before this one was an X. I was in match shootoffs. The barrel was free of obstructions.

 

[lloydx2]

Not true Jim. Case head only has to get to 400 to become to softer. I have seen this happen. You will not be able to tell with contraction test (pliers visegrips whatever) It will appear to be hard. But not so. With short cases like 6BR you have to be carefull. Make sure when they drop out they don't go into a tight container that will retain heat for any length of time. They need to fall on an open tray and kept separated. Just a thought.

 

[Keith Glasscock]

I was involved in an IBS match at 1000 yds. The shot before this one was an X. I was in match shootoffs. The barrel was free of obstructions.

That pretty much eliminates anything I can think of. I am very interested in anything you learn - It could save me a bad experience.