Mystic Precision
CGN Ultra frequent flyer
- Location
- Summerland, BC
And the gunsmith gave the rifle back?????
Jerry
Jerry
possible bad brass
- Thread starter pmatuk
- Start date
Congratulations. You win the internet. Well played, sir. Well. Played.
PM me your mailing address and I will mail you your gift certificate prize.
You have earned it. I am humbled and shamed by your obvious brilliance.
Richard.
Cameron SS
CGN Ultra frequent flyer
- Location
- Ground Zero
It looks like in the first picture there is some residue inside the case. What is that?
That looks like no over pressure I have ever seen. It more looks like the case was blocked inside and 100% of the gas came out the primer pocket. What did the face of the bolt look like?
That looks like no over pressure I have ever seen. It more looks like the case was blocked inside and 100% of the gas came out the primer pocket. What did the face of the bolt look like?
- Location
- Calgary, AB
Wow. Can you find out what his load was? (bullet, power, charge)
It was blocked, by a bullet ;p. I wonder what the velocity was?
new brass H4831 SC 35GR bullet is 160 woodleigh fed lr primer
he only fired the 3 rounds .He has pulled the rounds and reweighed and still 35 gr powder below the shoulder and only owns that pound of powder so no mix ups .also bolt face still looks clean with no erosion (yes suprised also ,havent seen it myself)
he only fired the 3 rounds .He has pulled the rounds and reweighed and still 35 gr powder below the shoulder and only owns that pound of powder so no mix ups .also bolt face still looks clean with no erosion (yes suprised also ,havent seen it myself)
- Location
- Calgary, AB
That seems to be a very light power charge. Where did he get the load data from?
Mystic Precision
CGN Ultra frequent flyer
- Location
- Summerland, BC
I believe the term is called "detonation"... way too little slow burning powder. The primer flash can arch over the powder charge igniting it at both ends causing an out of control burn.. Instead of burning, the powder explodes.
Why you NEVER go below min load unless you have a very good idea of what you are doing and with powders designed specific to low density charges. The load data in my Hrn manual lists H4831... he used H4831SC which has even lower load density. This is where less created WAY MORE.
That action survived a massive amount of pressure. Be thankful the shooter still has all the important bits and pieces attached. I still do not understand why the gunsmith would return that action. Personally, I would chop it up or make it inoperable.
It did its job admirably... you may not get a second mulligan.
Jerry
35 is a good Start load. 40 is about max.
Does not sound like it is a wrong powder issue. he only has one can. Any chance that can got contaminated with pistol powder earlier?
Mike the bullet and make sure it is the right diameter.
Are we sure of the actual caliber (chamber) of the rifle?
I once had a very badly blown primer in a Start load. 6.5x55. But nothing like this example.
If I had to bet, I would say pistol powder at work.
Does not sound like it is a wrong powder issue. he only has one can. Any chance that can got contaminated with pistol powder earlier?
Mike the bullet and make sure it is the right diameter.
Are we sure of the actual caliber (chamber) of the rifle?
I once had a very badly blown primer in a Start load. 6.5x55. But nothing like this example.
If I had to bet, I would say pistol powder at work.
How old is that one can of powder that he owns? If the powder is old it could be dried out. Even though it weighs 35 gr it could be 40+ gr by volume. I have seen this happen before (not to me). It resulted in a broken bolt handle, and having to remove the barrel. .308 case looked like a belted magnum at the base.
Cameron SS
CGN Ultra frequent flyer
- Location
- Ground Zero
I don't have my records handy, but I used to do ballistic testing under controlled conditions and probably fired north of 1200 rounds with low powder charges to simulate low velocity (long range) impacts on test coupons. In order to simulate various ranges from a fixed 15m firing point, we did everything from 20% of commercial load data minimums incrementally up to 140%+ for V50 tests. Hundreds and hundreds at the 40% or less range. We had a breach loading single shot universal receiver with proof testing barrels with 4" thick material at the chamber. Over pressure was not usually a safety concern but we did blow out a lot of primer pockets, but that was only on the extreme high end of loads, never on the low end. We did this with various cartridges from .223, several .30 cals, .50bmg, 14.5x114mmR and 20mm.
With the low volume charges, never once had a sign of over pressure. Every shot was chronographed and never once did a low pressure charge result in an unexpectedly high MV. Had lots of inconsistent performance because some times the powder was at the bottom of the case and others at the top, but never over pressure. To solve the inconsistency we used cotton balls to wad the powder down inside the case to ensure that the powder always had consistent orientation and distribution inside the case.
If your "detonation" theory is valid, I can't imagine how we wouldn't have had dozens of these 'detonations' if not more, especially because prior to using the cotton balls, we did some limited testing to explore how powder orientation affected MV and shot to shot consistency. We played around with how we chambered the cartridge to try and figure out what the ideal way to load a partially full case was.
The experiment we conducted was with a 30-06 and 155 gr HPBT MK and about 35 gr of H4831SC. We deliberately used a low charge to exaggerate the effect of powder movement in a less than full case.
We tried three different loading techniques, 25 shots each:
Holding the case bullet up and gently tilting and loading the case to chamber the round with as much powder to the bottom/primer side of the case as possible.
Holding the case bullet down and loading the case so the powder was as far away from the primer as possible.
Holding the case sideways and shaking it to evenly distribute the powder along the length of the case.
What we found was that the closer and more compact the powder was in relation to the primer, the faster the MV. Each method revealed an ES and SD that was more consistent than random chambering (sometimes up, sometimes down) of unwadded cases. Consistent wadding of the case resulted in an even greater reduction in ES and SD.
We duplicated the testing with .50 bmg, 700 gr AP rds and 8 grams of H50BMG powder. Uncontrolled loading resulted in poor ES and SD. Wadding improved both dramatically.
Neither loading technique in either calibre resulted in a single firing with evidence of overpressure. Most of the primers weren't even properly flattened against the face of the bolt.
If your theory is correct, I can't understand how this guy went 2 for 3 with blown primer pockets and we never had one.
If I could propose a modification to your theory, it would be to suggest that instead of the powder beginning to burn at BOTH ends, but perhaps it began burning at the wrong end, and the explosive train of burning powder and shock wave was moving towards the primer pocket, rather than towards the projectile. With the explosive train moving in the wrong direction the primer pocket would be hit much harder than a normal detonation, regardless of overall pressure generated. Then again, if the powder was burning from both ends, the explosive train would meet in the middle, and I would suspect that to cause a case separation instead of a primer blowout and 1 of the 2 bad rounds did separate. But again, with the tests that we did, especially with the .50bmg, I am surprised we did not ever see this with our low powder charge loads.
In closely scrutinizing those photos, I almost want to suggest that they could have been fired out of battery, but I am unfamiliar with that rifle/action. I can't picture how the head space could have been so excessive as to allow the base of the case to expand outwards that much. Maybe in a semi, but not a bolt. Alternatively, a manufacturers defect that resulted in excessively soft brass, or annealing, could explain why the case so readily yielded, but it wouldn't explain why there was space for the brass to yield into. Those case rims are seriously deformed. Has me scratching my head.
I would love to see a picture shown from the side of the cases instead of from the head stamp. I would also love to know the OAL of the 1st fired case compared to the 2nd fired case.
Regardless of what the smith said, I would not fire that gun again until I had a firm understanding of what happened, and I can't believe the smith OK'd the gun.
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What about slow ignition? Regular primer with hard to ignite powder like 4831, primer det has enough gas to lodge bullet in the bore before powder goes off?
99% of these KB's I see are mouse fart loads...cast bullets with pistol powders and likely something at the bench like a double charge, this one is odd....
99% of these KB's I see are mouse fart loads...cast bullets with pistol powders and likely something at the bench like a double charge, this one is odd....
This is an older comment from a test and development engineer at NAMMO Lapua Oy:
"Potential dangers are double powder charge, too low powder charge that
might lead bullet stuck into bore, primer failure that might lead to
SEE. SEE is also theoretically always present with low charge, high
volume case loads. "
"Potential dangers are double powder charge, too low powder charge that
might lead bullet stuck into bore, primer failure that might lead to
SEE. SEE is also theoretically always present with low charge, high
volume case loads. "
