Primer rupture help

[whitebread]

I had a primer rupture today and I am on a quest to find out why.

The load:
300 Win Mag
Hornady once fired brass
Neck turned (wall thickness of 0.012")
Neck sized (0.329" neck bushing > 0.0025" of interference with bullet)
Primer pocket trued (depth of 0.131" +/- 0.0005")
Flash hole uniformed to 0.080" & chamfered inside and out
Case trimmed to 2.608" & chamfered inside and out
Winchester WLRM primer set by hand
Markron primer sealer applied after seating
65.0 grains of IMR 4350 (trickled)
Nosler Accubond 200 grain set 0.050" off lands
3.5265" COL
No crimp

The rifle is a Hill Country Harvester Plus (24" bbl, R700 action). The bore condition was 161 shots and in copper equilibrium. The bolt face is now eroded where the gases escaped.

The loads first ten loads chronographed at 2766 fps with a standard deviation of 8.6 fps (82F). The 11th shot ruptured the primer and it chronographed at 2715 fps. I shot the following 4 cartridges before I noticed the brass. And no, the cartridges were not sitting in the sun.

Can anyone venture a guess as to what caused this? Any input on how to avoid this in the future? I am a bit concerned about this. Thanks.

 

[HodgdonExtreme]

Winchester primers do that, search around and you'll see this same topic comes up ~twice a month.

Switch primers, problem solved.

Sorry to hear they ate your bolt face.

 

[whitebread]

Sorry - I searched and didn't find anything.

So, anybody need ~4500 WLRM primers?

 

[Niles Coyote]

https://www.google.com/search?lr=&h...re+pressure++site:snipershide.com&btnG=Search

 

[1SMALLJOHNSON]

Somethings wrong, and I suspect it's your chamber/bullet seating depth. According to a reputable website, IMR 4350 should generate ~ 62,500 psi at 69.5 grains. You're at 65 grains. According to my red-neck math, you should be at about 55kpsi with that load of 65. However, you're definitely generating more than 55kpsi. Have a look at the craters around your firing pin strikes. You've already got pressure signs, and you're not even up at the higher charge weight. What chamber did your man put in that gun? I suspect it's a tight neck, tight leade? No problem with that, but you've got to play the hand your dealt! Now, there's an important thing to understand about .300 Win Mag: There is no straight-dimension throat. Rather, it's a constant taper. Therefore, while you record your free-bore of 0.050" off the lands, it ain't exactly so. Have a look at your reamer print, and see if this is true. If so, you don't have as much "breathing room" as you think you might have.

Please understand, I'm not bashing you, nor your gun. I'll bet that thing will shoot like a house afire, if you just get the right combination. I'm just saying that you're likely generating a lot more pressure than you suspect. I"m happy to help you diagnose the issue, and we can handle it off line if you wish. Just PM me, and we'll see if we can figure it out together.

 

[milo 2.0]

I wouldn't rule out that shit Hornady brass either.

 

[Dan Newberry]

indeed, it's the primers... don't bark up any other trees, we've seen too much of this lately... go with Federal or CCI and it'll be all better.

 

[HodgdonExtreme]

Here's some other threads:
http://www.snipershide.com/shooting/snipers-hide-reloading/143977-leaking-primers.html
http://www.snipershide.com/shooting/snipers-hide-reloading/246570-blowing-primers-minimum-load.html
http://www.snipershide.com/shooting...erced-primers-picture-inside-help-needed.html

You'll see the common themes are known good and/or moderate loads, winchester primers, pinholes on the outer radius...

 

[supercorndogs]

was the bolt hard to lift on that shot. is that black circle an extractor swipe. the primers look normal. all my 700s do that because of the extra space around the firing pin. if pressure ruptured it you will see sighs in the brass. hard bolt lift extractor swipe. all the loads i have seen blow the primer significantly stretched the base and primer pocket to the point the primer fell out. i would suspect the primer to be at fault not pressure.

 

[1SMALLJOHNSON]

If you have a look at the edges of the primers that have been fired, you'll note that they're no longer radiused. They're now square. I would ask the OP to prime a shell, load no powder and no bullet. Fire that primed shell in said rifle, and take a picture of that fired brass. Let's see the result?

 

[rduckwor]

That is a classic Win primer rupture right at the transition from base to sidewall. Its the primers, nothing more.

Good Luck,

 

[whitebread]

Thank to all for the help. I have an email into Winchester to see what they say. I did order 5k of the CCI primers and I will switch over to those.

1SMALLJOHNSON, the craters may be a tad big, and as you say the load is on the low side. I will seat the bullets deeper and see what happens. If that doesn't reduce the craters, I may be PM'ing you. Thanks.

 

[former naval person]

Remington bolts do that primer "cratering" thing. I've been informed that it a factory design in order to decrease leakage in the event you get a primer puncture in the center. I had my rifle bolt bushed.

 

[Mad_Charlie]

It is just the very famous Winchester large rifle primer blowout. Those fired primers don't look too overpressured to me, and the "crater" is a Remington trademark.

 

[whitebread]

I spoke with Winchester. They sent a call tag for the blown primer, my existing primers, and any loaded ammo using those primers. I will post back with the outcome.

 

[DAVETOOLEY]

An all to common occurrence with all primer manufacturers over the last three decades. It just happens. I've seen as high as a 5-10% failure rate. It's the metallurgy of the primer cup. Nothing else.

 

[HodgdonExtreme]

An all to common occurrence with all primer manufacturers over the last three decades. It just happens. I've seen as high as a 5-10% failure rate. It's the metallurgy of the primer cup. Nothing else.

Dave, as always we appreciate your presence and experience here.

What other primers have you seen this issue with prolifically (not just ONE in a blue moon)?

I've only been into rifle reloading since ~2007, but since then, it seems Winchester is the "usual suspect" for this problem.

 

[DAVETOOLEY]

Federal Remington CCI Winchester. There's not a pattern as to make model or prominant manufacturer.

 

[1SMALLJOHNSON]

OK, I'm going to retract part of my statement, but re-confirm another part: If a primer manufacturer "pinch-trims" the lip of the primer cup, and leaves a jagged edge (like a burr), or if that locally worked area becomes "work hardened" compared to the rest of the primer cup, then a leak, with no associated "high cartridge pressure" could certainly occur. In addition, if there's a radius at the base of the primer pocket, then the likelihood of a gas leak at the primer/primer pocket interface increases.

But, we've got two additional pressure signs associated with the OP's pictures:

1: The primer radius is squared off. Not a sign of "high" pressure, but certainly a sign that you've exceeded some "minimum" loads. His present load is considered mild, but the squared primer does not indicate a mild load.

2: Primer cratering. At 64,000 psi, it's likely that you're going to START to see some evidence of cratering. But with these primers, there's some DECENT evidence.

Thus, if it were me, or if I were asked to assist in diagnosis, I'd ask the OP to check the reamer print and see if his particular reamer was a tight throat/short throat. I'd also recommend to get a read on those primers fired without propellant pressure.

I certainly respect the opinions of the people on this board. I'm just saying that those craters would cause me pause. Having a gas leak, more pause. Don't tickle the dragons belly, unless you REALLY know what you're doing.

 

[Bradu]

An all to common occurrence with all primer manufacturers over the last three decades. It just happens. I've seen as high as a 5-10% failure rate. It's the metallurgy of the primer cup. Nothing else.

I ran into this with Winchester primers in my AI last year, the bolt face has several pits. At what point would you recommend having the bolt face repaired?

 

[DAVETOOLEY]

It may look ugly but it doesn't affect the performance or safety of the rifle since it's away from the firing pin hole. If you start burning the edge off the firing pin hole by piercing a lot of primers then a domino effect will be in play. The more you pierce the more primers will pierce as the edge erodes.

 

[whitebread]

To give a conclusion regarding Winchester for those that find this thread in the archives:

1) I submitted an inquiry via Winchester's website.
2) The next day they called to discuss the problem.
3) Winchester immediately sent a call tag for the existing loaded ammo.
4) Winchester sent a box to ship the primers back in.
5) When I received the box for the primers, Winchester initiated a pickup.
6) I received a letter in the mail describing the problem and that the returned product was being examined by the Quality department.
7) Said letter also included a check to cover replacement of the returned items and a bit extra for inconvenience.

Exactly 1 month from start to finish.

 

[oldfudd]

As I've stated on a couple of other threads, I've had this issue occur several times on LC brass when I've used Winchester LR primers. Changed to CCI and the problem has disappeared. However, I have not had any issues with Winchester large pistol primers, but I'm snake-bit now and have quit using all Winchester primers in general.

 

[BuzzBoss915]

I'm reading a lot about Winchester primer failure, usually LR. I have to shake my head if this is really a component issue and Winchester has not addressed the matter with the urgency deserved.

Aside from that, I have shot 300WM for many years, strictly as a hunting gun although it is very accurate and completely stock, except for the stock. I have used some 4350 but almost all of my hunting loads are with H4831 and I use the Winchester LR primer which is a little hotter than other LR primers. I have never felt the need for magnum primers in 300WM, over the 120 8 1/2 LR primer.

Mag primers may be a solution with very slow burning spherical propellants under cold weather conditions, but in my opinion, you are defeating the slow burning characteristics of IMR 4350 with that mag primer and I think there are better choices available, as far as powder.

Of course, none of the above addresses your problem, but....for what it's worth. BB

 

[bax]

Are there two holes? I see a little one in the primer shoulder and a bigger dark spot that looks like a hole -- or -- the spot where the ejector pin was?

 

[MtnCreek]

Are there two holes? I see a little one in the primer shoulder and a bigger dark spot that looks like a hole -- or -- the spot where the ejector pin was?

When the primer ruptures, carbon fouling fills any voids (at ejector, between primer / case head, headstamp).

 

[Clark]

QL thinks the velocity will be what the chrono says it is, and QL says the pressure is 57.5 kpsi.
When the velocities match, QL pressure is always dead on.
I don't know about the leaker, but all of those primers look too cratered for that pressure.
Either the primer cups are too thin or the firing pin is too light, or the firing pin to firing pin hole fit is too loose.