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Blown out primer!

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Post Options Post Options   Thanks (0) Thanks(0)   Quote Zed Quote  Post ReplyReply Direct Link To This Post Posted: October 22 2014 at 11:33am
I also had a very slight mark on the bolt head face after the blown primer. Continued to use it without issue, but have now find a bolt head of higher number to correct the headspace which was on the upper limit.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Gun Nut 4 Quote  Post ReplyReply Direct Link To This Post Posted: December 18 2015 at 4:12am
I picked up a bunch of R-P cases once, I had one devil of a time de-priming them, their  flash-holes were too small for the de-priming pin. It maybe that this particular case had a smaller flash-hole than the rest of them. Was there any problem de-priming it?
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Zed Quote  Post ReplyReply Direct Link To This Post Posted: December 18 2015 at 4:17am
I use a home made de-primer, as I remove the primers before cleaning and preparing the cases. However there are times when the primer resistance to push out is different. In the case of the blown primer, I did find evidence of damage to the pocket, which I believe was the cause. Not had any issues since.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Gun Nut 4 Quote  Post ReplyReply Direct Link To This Post Posted: December 18 2015 at 4:31am
Having read a few more comments, I see it was a head-space problem. I almost asked if you were noticing any blackening of the cartridge neck. I'm glad you were able to isolate the problem and correct it. Those good old No.4 Mark I bolt-heads, they are enough to keep me leaning towards the Mark III's and the Pattern 1914's, in spite of the large variances in their bore diameters. They shoot find if you can match the bullet to the particular bore diameter, and a lot better than having a case-head separation while in the field, without having the tool to remove the fractured brass.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Zed Quote  Post ReplyReply Direct Link To This Post Posted: December 18 2015 at 9:35am
Luckily I've never had a case separation during a competition; but I do have the extractor and it's always within reach if I need it. That said; I'm more attentive of the case condition now and inspect each one after cleaning. As soon as the "ring of death" starts to show around the base; they are junk. Once you've got the eye for it; it's easy to spot.
Regarding the headspace; I have since bought some proper gauges and it was good on the field gauge at 0,074" but just failed the no-Go at 0,70". It now passes both of these with ease.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote W.R.Buchanan Quote  Post ReplyReply Direct Link To This Post Posted: December 18 2015 at 9:54am
I have had exactly one blown primer in my life and it happened to me last year and scared the pooh out of me.
 
It was a .30-06 round loaded in a once fired Federal Case. an 85-90% load.  It happened in my Ruger Guide Gun which had less than 50 rounds thru it at the time. I had to open the bolt with a plastic mallet, and after several of us inspected the gun we deemed no problem and I continued to shoot with no further incident.
 
However I did start a different box of ammo as I was now not sure of that batch.
 
The Primer Pocket was .250 after firing IE: it was destroyed, and the primer and all debris went right out the vent hole.
 
When I got home I pulled all the remaining bullets and pushed the primers out and found three out of the 30 or so left had loose primer pockets and the primers pushed out easily. I used a Lee Depriming Punch and Base and a small Sinclair Arbor Press to do this.
 
After measuring those 3 I found them to be nearly .211 and since the WLR Primers I was using measure .2105 that could have been the part of the problem.  Primers do swell when fired and most of the fired ones on the floor are nearly .212 so I wasn't sure exactly what was going on.
 
My remedy was to run all of my Once Fired Federal Brass, all of which was used to test fire Rebuilt Garands, thru a Dillon Primer Pocket Swager.
 
It is common machine shop practice when you ream a hole and it comes out big, to put a ball bearing over the hole and smack it.  The result is the ball swages the entrance of the hole down a little.
 
The Dillon Tool does essentially the same thing when it radiuses the mouth of the pocket.
 
The other thing I did was stop using the priming function on the PW Metal Matic II press I was using as it provided no feel as to how much pressure was required to seat the primer.  I use an RCBS Lever type tool now and it is the best priming tool I ever used.  I can do 50 cases in 3 minutes easy and feel the pressure on every single one.
 
After swaging the pockets on my brass I have not had any primers push in with light pressure, and needless to say no more blow ups..
 
Randy
 
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Post Options Post Options   Thanks (0) Thanks(0)   Quote pogson Quote  Post ReplyReply Direct Link To This Post Posted: July 12 2018 at 6:38am
There's lots of good information here. I'll add a bit of mine...

One thing that has not been mentioned is that high pressures can weaken cases and upon repeated firings things can go wrong: split necks, body ruptures, head separation and primer pocket enlargement. Keep pressures down to the level you need rather than maximum. For hunting, when I know I don't need maximum range, I reduce charges a few grains to give longer case-life. I have some cases I've been firing since the 1970s.

Even if charges are set within safe limits there is another way things can go wrong, powder bridging. The stick powders particularly can jam up in the powder measure and dump an incomplete load in one case and an excessive load in the next case. These days, with an electronic powder scale, I weigh each charge. This also benefits accuracy because my measure, with my best powders, throws charges +/- 0.5 grains. A powder bridge can greatly exceed that variation. In the worst cases I've had a thrown charge fill a case to overflowing. I've long inspected my charges by peering into each charged case with a small flashlight or inserting a rod into the charged case to check the level of the powder. Now, with the fast electronic scales, I just weigh each one. Groups are smaller. Deer are just as dead.

303 British has not nearly as high a pressure as other cartridges like .308 or .30-'06, so seeing cratered primers and flattened primers suggests some of these pictures are showing loads far too "hot". On the other hand, very light charges can sometimes detonate or show pressure spikes. That's why reloading manuals show starting loads higher than expected for some powders. Many powders don't burn reliably at lower pressures as might be found near starting loads in 303. Some manuals start automatically 10%, 5% or 3% below maximum. I would not use 10% low with any slower powder like 4350 in 303. It might be OK with 3031 to 4895. For hunting I generally work 1 or 2 grains below maximum because I want to keep my cases longer and I know my trajectory will reach out and touch deer effectively as far as I can see them in my usual spots.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote W.R.Buchanan Quote  Post ReplyReply Direct Link To This Post Posted: July 13 2018 at 10:41am
The secret to long case life in the .303 is to only neck size the brass. 

 I use a Lee Collet Style Neck Sizing Die, about $15 from Titan Reloading or a dealer near you.

My gun has one of the "generously" sized chambers we all know about, and it moves the shoulder of the case forward about .060+ It also reshapes the shoulder to something about .060 long and at a 45 degree angle. Good thing the case headspaces on the rim cuz there ain't much shoulder.

Pushing it back to original with a F/L die only makes the case separate on the second or third firing. 

The good brass out there is PPU as far as I can tell.

Randy
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Stanforth Quote  Post ReplyReply Direct Link To This Post Posted: July 13 2018 at 2:38pm
I have experienced similar faults in one of my Remington Rolling Block rifles, 7X57 Mauser.
 
In all cases it was with Winchester cases. Never any other make. I binned all my 7X57 Winchester cases which was distressing as that calibre is ultra hard to find in the UK.
 
No more problems.
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