6.5 PRC over pressure question

[songdog204]

I was wondering if anyone had an idea as to what might have happened here. 147 eldm over 59g of retumbo and CCI mag primers. I've shot about 60 rounds so far with no signs of pressure and suddenly had one blow up. What confuses me is the lip that formed by the case head (kinda looks like a belted mag). It's possible I made a mistake but there's no way to double charge a 6.5 prc case with retumbo and I'm using an RCBS Chargemaster lite. FWIW I'm using Nosler blem brass. Any thoughts to what might've happened?

 

[Doom2]

Is it possible a faster powder was left in the dispensing tube of the Chargemaster?

 

[coop2564]

Possibly brass had smaller volume area due to thick side walls or something was inside brass like tumble media etc. leaving less volume area for charge. Weigh the brass and compare to the others that had no problem, might tell you if that piece is thicker, you could do a water volume test as well.

 

[songdog204]

Is it possible a faster powder was left in the dispensing tube of the Chargemaster?

Doom: that crossed my mind but it was in the middle of a batch I had loaded and wasn't one of the first ones after a powder change.

Coop:
I will check on that this evening. The brass is supposed to be cosmetically blemished but there's a good chance something like that happened. I'll report back what I find

 

[Benchrest Braxton]

Just a few ideas:

Bad piece of brass

Carbon ring

Change in environmentals?

How close are you to lands, maybe you jammed one?

 

[Another Casual]

Hornady data shows a max of 58.5, hodgdon shows 58.8. I doubt 0.5 over would result in this.

 

[songdog204]

So here are some more pics and measurments of the faulty brass

These first 4 are obviously the ones in question. Also take a look at the primer pocket. This is a large rifle primer that was in my tray and there is an excessive amount of space.

 

[songdog204]

Here's a comparison to a piece that was shot the same day.

Doesn't seem to be a huge difference. However, if you can tell on this primer pocket, there seems to be a "ring" on the outer edge. That "ring" is what I'm going to say is no longer on the piece that was over pressure. So would it be safe to assume that it really was just a faulty piece of brass?

 

[coop2564]

The outside diameter is not the problem its the inside diameter that would cause the pressure. Being you are already over book pressure a case that has less volume inside due to thick walls could cause the problem. If you put a primer back in high pressure case, put case on scale and zero scale and fill to top with water and write down that weight and do same for one that shot ok and compare water weight of the two, that will tell us more about the case volumes. If the high pressure case has less room (water weight) and you are already slightly over max. Boom.

 

[parshal]

I had the exact same thing happen in a 6 Creed. Shot 33 or so from a batch of 50. I was shooting them in order of loading. I never did figure it out for certain although I did discover excess bolt to recess clearance.

 

[Greyfox]

Possible causes:
-Faulty case(Nosler blemish?)
-Media left in the case, under powder-late ignition.
-Powder overcharge

 

[jrock]

I bought a few hundred cases of Nosler blems and have see issues that are more than cosmetic. I've see thin walls and cases that are significantly heavier than their brothers. I've had to toss about 15% of the cases because of physically defects. The savings on Nosler blems aren't in it for me to deal with the issues when they arise.

 

[songdog204]

The outside diameter is not the problem its the inside diameter that would cause the pressure. Being you are already over book pressure a case that has less volume inside due to thick walls could cause the problem. If you put a primer back in high pressure case, put case on scale and zero scale and fill to top with water and write down that weight and do same for one that shot ok and compare water weight of the two, that will tell us more about the case volumes. If the high pressure case has less room (water weight) and you are already slightly over max. Boom.

I'll do a little more testing tonight. I can't put a primer back into it because the pocket is so loose. Might try hot glue in each to keep the comparison as close as possible

I bought a few hundred cases of Nosler blems and have see issues that are more than cosmetic. I've see thin walls and cases that are significantly heavier than their brothers. I've had to toss about 15% of the cases because of physically defects. The savings on Nosler blems aren't in it for me to deal with the issues when they arise.

thinking I'm gonna have to measure case capacity on all of them and determine which ones are good and which ones to toss if coops theory is right

 

[Legionnaire]

Shot from a bolt action, correct?