Kaboom 💥 Today 😟

[can1010]

your neck tension is a non-issue. benchrest guys have used very light neck tension and load bullets long and let the bolt close to set bullet. your .007 neck clearance while not ideal would be a cracked neck issue. you should not be bumping your shoulders on fresh fireformed cases, chances are problems from bad fireforming and to much bump will cause problems in the future but very rare on second firing. my biggest question is why did the thickest and toughest parts of the brass shatter like that. the case head shattering in half like that is a first for me.

 

[DoneNOut]

I agree. But was the OPs chamber cut that way?

99.9% sure. When I switched to Redding dies to size the 708 cases did have resistance on bolt closure. I think Vince is right again. With my RCBS dies I was able to size the shoulders further.

 

[akdad]

Someone has already mentioned it but cutting the case shot right before may help clear things up especially if they are all same lot.

 

[Culpeper]

Didn't primer pockets feel loose this go around?

 

[Hugnot]

Bad brass

Real clean & smooth break just above extractor groove. Not a head separation caused by excessive head space

My guess is that the defect existed when that piece of brass was new, but the piece of brass survived the first firing - it is "once fired brass". Upon making the Ackley Improved "708AI" the brass was subjected to a crush fit, like .004. Upon being subjected to a crush fit the imminent brass failure or defect was subjected to right angle compressive force by the crush fit. This force increased the existing stress fracture that was indicated by the clean & smooth break. Photos show the defect was radial, like all around the inside. A normal piece of brass could withstand the crush fit. The brass head was work hardened during manufacturing and during this process the compressive stress fracture was initiated, just waiting for more compression followed by stress fracture then failure.

 

[DoneNOut]

Didn't primer pockets feel loose this go around?

Nope

 

[Allen Kitts]

Wow buddy that is very scary and I am so glad you made it out of this with just a minor injury. I have seen more brass than I care to mention separate in the chamber but never there and like that. Could have been so much worse. Again glad you are OK.

 

[ButterBean]

Like many here, I've been loading over 50 years, with many wildcats. Never seen that?

Glad you're OK!

I'd guess a bad piece of brass. Too regular in appearance for a common pressure failure?

I've never seen that either, I've had em separate but never destroy a case head

 

[DoneNOut]

I'm still having a hard time accepting that me pushing shoulders back .001-.003 too far on the fire forming loads on 1X fired brass would cause a case rupture. Heck 300WM cases stretch the shoulders .018" upon initial firing.

I always seek to find fault in myself. As you have read thus far. There is however the notion I didn't screw up. This kind of thing drive a guy mad! LOL

 

[Culpeper]

I'm still having a hard time accepting that me pushing shoulders back .001-.003 too far on the fire forming loads on 1X fired brass would cause a case rupture. Heck 300WM cases stretch the shoulders .018" upon initial firing.

So, sized 308 Win to 708 and accuracy was good for 200 rounds. Then after fireforming you had accuracy issues?

 

[Old Rooster]

Bad brass

Real clean & smooth break just above extractor groove. Not a head separation caused by excessive head space

My guess is that the defect existed when that piece of brass was new, but the piece of brass survived the first firing - it is "once fired brass". Upon making the Ackley Improved "708AI" the brass was subjected to a crush fit, like .004. Upon being subjected to a crush fit the imminent brass failure or defect was subjected to right angle compressive force by the crush fit. This force generated a progressive stress fracture that was indicated by the clean & smooth break. Photos show the defect was radial, like all around the inside. A normal piece of brass could withstand the crush fit. The brass head was work hardened during manufacturing and during this process the compressive stress fracture was initiated, just waiting for more compression followed by stress fracture then failure.

If there was resistance the problem had to be with the brass.I am with Hugnot.
Nothing in this world is perfect,not even Lapua

 

[Hugnot]

I just got a 100, 1x fired .243 Lapua brass. Would my primary health care provider be annoyed if I asked her to have them X-rayed?

Inspecting the brass with a bore scope might work.

 

[trout004]

Does your brass show thinning at the head when cut in half? Here is a 300 WM case that shows significant stretching.

 

[243winxb]

Very high pressure made the case head disappear.

Was it a donut, plus bullet jammed into rifling?

Or the low neck tension allowed the bullet to move out of the case to soon. This may cause a 2nd pressure spike. It acts like a plugged barrel.