Non-firing ammunition issue???

[MarinePMI]

I'm not convinced that the case shoulder can be set back so far with standard dies as to cause a weak or inconsistent primer strike. Think how much the firing pin actually protrudes.
If it was possible for the firing pin to drive the case forward so much clear of the boltface as to result in a partial strike, then I think there would be a dangerous headspace condition.
Rifles could then be blowing up all over the place, so sorry just not buying this at all.

You are (of course) entitled to your opinion. That being said, I've seen it enough to know it happens. It's all about stacking tolerances. Some dies (with press, and shell holder) will let you bump the shoulder too far back. It's also the reason, radical wildcat case forming involves seating a bullet into the lands when the formed case shoulder is either small or a guestimate. (.17 Ackley Hornet comes to mind, with it's false shoulder in an un-fireformed case.)

The case may fail, but likely what happens is it has case head separation on the 2nd or 3rd reloading. Cartridge brass is pretty ductile when new and annealed, and will allow for a lot of user error when reloading.

As far as excessive headspace, well, excessive headspace doesn't imply (automatically) a catastrophic failure. Rather, it describes a condition. One that may, or may not, be dangerous. That may, or may not, cause the receiver to fail in holding in that spike of pressure.

But as I said, everyone is entitled to their own opinion; even if it's wrong. <shrug>

 

[Andy seatrout]

Right, little later than planned as I spent last night drowning my xc90 and then ferrying three strangers past floods all around Powys…

Examination on the round that misfired, excuse the mess but it’s a multifunctional workshop space and I’ve got to hoover it back to proper clean condition …..

NB; photo of press with primer seater shown…photos in no particular order as I’m not smart enough…..

1) Bullet pulled…. Nothing untoward
2) powder in case tipped out and weighed
3) photo of primer hole inside case looks very clean
4) strike seems ok, seating depth ok?
5) primer removed ( safety goggles worn)
6) photo of primer that I think has actually just failed to go off at all.
7) embarrassing confirmation of primer make; not CCI but S&B

Conclusions anyone? Too much headspace= light strike? Faulty primer?

Andy

 

[Andy seatrout]

Press photo showing primer ‘ram’ and primer extracted

 

[MarinePMI]

From the scratches on the primer, I'd guess that the primer was not seated fully. It appears as if the bolt left the scratches on the primer as it rotated into battery, with the primer standing slightly proud. Just a guess, since trying to diagnose this from 9,000 miles away is always difficult.

 

[Andy seatrout]

I welcome all opinions, I’m pretty new to reloading and keen to learn…. If I want to do something, I want to do it well….

 

[Utectok]

**** primer

 

[Andy seatrout]

**** primer

Being new to this, is that a scientific explanation?

 

[Utectok]

Being new to this, is that a scientific explanation?

indeed lol Ive never had cci lrg rifle not go bang for what it is worth

 

[Andy seatrout]

Well, I went back to basics; reset the full length seating die, changed out my older callipers with some new ones ( still made in china but seemed to be more consistent…..

I took the modified case as a datum, I cross checked this against a Hornady factory round (superformance 140SST) they were exactly the same to the 1,000th…..using the Hornady case comparator….

Then measuring fired cases they averaged pretty consistently 0.0004 longer than the datum, the ‘misfire/ light strike’ cases I had from the start of this week, and found they were 0.0006 inches shorter than the datum…. So 0.001 too short….too much gap…

I changed from S&B primers to Magnatec - to remove the ‘dodgy primer’ element- I had kept the die the same- and there were some light strikes (2 in 40 rounds failed to go off).

So adjusting the die to return a fired case to zero on the datum ( Lapuau new cases were minus 0.0001) I loaded 44.7gr of RS60 powder with Nosler expansion tip copper in 120gr…. Which seemed to shoot very sweetly….

No chronograph today as it was frankly dark and raining, but 40 rounds and not a hint of a misfire or light strike. So less lubricant, don’t handle primers, and leave the die alone now…

Every day is a learning day…. But I was happy enough with the results off sticks in a downpour at 85 yards…..

 

[phaedra]

I've had problems with both S&B and Magtech SRP taking 2 strikes to go off in both my 300 BLK's

No problem whatsoever with CCI or Federal SRP, the S&B and Magtech have harder/thicker cups, the Magtech 7-1/2's are regarded as Small rifle magnum primers.

In my case using sub-sonic loads the case doesn't fully obturate in the chamber which can result in it being pushed forward from the bolt by the primer, this bumps the shoulder back..

Fired the last of them off yesterday using full loads, shoulders are all now back to where they should be.