Yes. These monolithic lathe turned copper bullets were HBN-coated by me prior to loading/shooting.
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Blew a Primer _ Analysis
- Thread starter Pdvdh
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elkaholic
Well-Known Member
Paul..... I just saw this post which is of great interest and may answer my question as well.
This fall I had developed a load for my 30/375 with a new powder (n570). I ran a ladder test at about 75 degrees with the magneto speed. I chose a load 3 full grains under the top load which had a faint extractor mark (easy to do on Hornady brass).
This fall, I fired 2 consecutive shots with no signs of pressure notated even during extraction or ejection but when I picked the brass up, the primers had dropped
WHAT?? The temp was about 42 degrees
which should not have been a good reason for this. Being a new powder, I did not know what to think. My plan was to try to duplicate conditions and further
test. The brass was near New and
showed no signs of problems the first
firing!.
Without any further comment, I think you may be spot on with the bad brass theory! You, Jace, and myself had discussed the quality of our latest lots of
brass earlier and it seemed that primer pockets we're getting loose prematurely.
FOR THE RECORD:. That is NOT TOO MUCH VELOCITY FOR THAT CARTRIDGE!
This fall I had developed a load for my 30/375 with a new powder (n570). I ran a ladder test at about 75 degrees with the magneto speed. I chose a load 3 full grains under the top load which had a faint extractor mark (easy to do on Hornady brass).
This fall, I fired 2 consecutive shots with no signs of pressure notated even during extraction or ejection but when I picked the brass up, the primers had dropped
WHAT?? The temp was about 42 degrees
which should not have been a good reason for this. Being a new powder, I did not know what to think. My plan was to try to duplicate conditions and further
test. The brass was near New and
showed no signs of problems the first
firing!.
Without any further comment, I think you may be spot on with the bad brass theory! You, Jace, and myself had discussed the quality of our latest lots of
brass earlier and it seemed that primer pockets we're getting loose prematurely.
FOR THE RECORD:. That is NOT TOO MUCH VELOCITY FOR THAT CARTRIDGE!
I hope so too, and I'm sure more than you!
I thought about your experience, and will continue to keep that in mind going forward. That's a bad experience for sure. Appreciate that you shared it in the other Thread.
elkaholic
Well-Known Member
Hi Rich,
Thanks for your input.
The 8x68S RWS brass is looking much more attractive to me after this blown primer. I can buy a lot of the stronger, higher quality RWS brass for much less expense than the cost of a new BAT bolt. The nitride surface on the bolt face seems tough, but it can only take so much torch cutting...
It may be time to move on with the purchase of some stout RWS brass. Trying to find some positive in the aftermath of this experience. Blown primers can be motivational moments!
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MudRunner2005
Well-Known Member
This happened to me back in 2014 with my .25-06 AI with 7828 SSC.
After racking my brain and asking questions on here, I took all the info given and have come to this conclusion... This is NOT 100% fact, this is just simply my own conclusion and opinion.
It is 100% a pressure related issue caused by a spike in chamber pressure. That is your guaranteed "for-sure" problem. The next is deduction to figure out where the pressure spike came from.
It seems that some cartridges mask pressure signs well with slow-burning powders and heavy-for-caliber bullets, and you don't know you've crossed the line until you have a pressure spike that shows detrimental override, like a blown primer.
Another possibility to cause pressure spikes, is the case might be too long, and is getting pushed into and pinched in the leade of the chamber. If this checks out, trim your brass, and see if the issue persists.
Another, is inconsistent seating depths, and the bullet happened to get a bit too close to the lands and caused a spike. This can be caused by inconsistent dies, inconsistent bullets, inconsistent neck tension, highly-compressed loads, or any combination of the above. This is why I try to apply equal pressure and speed when seating my bullets, and let the ram sit at the top for a couple seconds before lowering it after seating the bullet to give the brass time to settle and not push the bullet back out any. And I also check each loaded round afterwards with my calipers and a comparator to ensure concentricity.
Another possibility, different lots of powder can have slightly different burn rates, and sometimes if you run out of one lot, and use powder from another to complete your loading, this can happen.
All of these can cause pressure spikes and issues like this. I would go back and check and see what you can figure out. Also, that's a big cartridge, and when you stress a magnum-sized cartage with that much pressure, that can cause problems. I'd have that rifle pulled apart by the gunsmith and get it magna-fluxed to ensure there are no stress fractures that you can't see with your eye. That's what my smith did with mine, and luckily nothing was damaged.
After racking my brain and asking questions on here, I took all the info given and have come to this conclusion... This is NOT 100% fact, this is just simply my own conclusion and opinion.
It is 100% a pressure related issue caused by a spike in chamber pressure. That is your guaranteed "for-sure" problem. The next is deduction to figure out where the pressure spike came from.
It seems that some cartridges mask pressure signs well with slow-burning powders and heavy-for-caliber bullets, and you don't know you've crossed the line until you have a pressure spike that shows detrimental override, like a blown primer.
Another possibility to cause pressure spikes, is the case might be too long, and is getting pushed into and pinched in the leade of the chamber. If this checks out, trim your brass, and see if the issue persists.
Another, is inconsistent seating depths, and the bullet happened to get a bit too close to the lands and caused a spike. This can be caused by inconsistent dies, inconsistent bullets, inconsistent neck tension, highly-compressed loads, or any combination of the above. This is why I try to apply equal pressure and speed when seating my bullets, and let the ram sit at the top for a couple seconds before lowering it after seating the bullet to give the brass time to settle and not push the bullet back out any. And I also check each loaded round afterwards with my calipers and a comparator to ensure concentricity.
Another possibility, different lots of powder can have slightly different burn rates, and sometimes if you run out of one lot, and use powder from another to complete your loading, this can happen.
All of these can cause pressure spikes and issues like this. I would go back and check and see what you can figure out. Also, that's a big cartridge, and when you stress a magnum-sized cartage with that much pressure, that can cause problems. I'd have that rifle pulled apart by the gunsmith and get it magna-fluxed to ensure there are no stress fractures that you can't see with your eye. That's what my smith did with mine, and luckily nothing was damaged.
elkaholic
Well-Known Member
Sorry that happened! If you had not experienced this, I would not have thought the brass was that bad! I have NEVER had brass go south like that so I was looking elsewhere?
Nothing cryptic there, it means exactly what it says.
elkaholic
Well-Known Member
Those are all possible causes but given the fact that it just happened to both of us with different powders, bullets, etc, I would say there is a 90 percent chance it was brass! I have 1100 rounds with no issues until I used a new lot of brass this fall.
elkaholic
Well-Known Member
I'll take a few more measurements on the fired casing. Will double check some things to the extent I can. I'm confident the case length wasn't excessive, but will measure the fired case length to establish the certainty of it.
Higher pressure should have yielded higher MV, no? The LabRadar confirms substantially less MV on the case with the blown primer. The reduced MV is in line with the reduced powder charge and the anticipated lesser pressure.
This is why I initially, and tentatively, point the finger at the Hornady casing.
Higher pressure should have yielded higher MV, no? The LabRadar confirms substantially less MV on the case with the blown primer. The reduced MV is in line with the reduced powder charge and the anticipated lesser pressure.
This is why I initially, and tentatively, point the finger at the Hornady casing.
