I've also seen this post by Norman Johnson before, and mostly agree with his conclusions. The only thing I question is his definitive statement that S.E.E. can only happen with reduced charges of slow burning powder. While powders like H 110 or WW 296 aren't near as fast as Bullseye, they are a lot quicker than some like 50 BMG. And some people who report S.E.E. problems seem to have had more problems with reduced charges of fast burning powder in bottleneck cases rather than in straight walled cases. But that is hearsay that I can't prove or confirm. If those incidents were actually from double charges, they should be equally distributed among fast and slow powders and straight or bottleneck cases.
I was surprised to see his root cause #3 come under suspicion here. If the cases were only on their second loading, I wouldn't expect much if any neck thickening due to firing or resizing/expanding.
I assumed that the pressure might have jumped a bit above the advertised 30,000 psi due to going slightly over max overall loaded length. But that didn't really set off any alarm bells with slight engagement of the rifling with a bullet cast of Lyman #2 alloy. What does jump out is the comment about the bolt being hard to close due to that into the lands seating arrangement. I wouldn't think slight engagement of the lands would add much effort to closing the bolt. But of course, I don't know just how much extra effort was involved. I've seated jacketed bullets to a point that they would leave slight land marks on the jacket, and that didn't add much effort at all to closing the bolt.
It's obvious that you are hardly a novice reloader Brent, so I believe you when you say headspace was not an issue with nearly new brass. So for the head to completely separate from the case, it had to be unsupported. That would mean either the bolt got set back or the bolt moved rearward because the lug recesses shattered. Can we assume that the safety lug is the only thing that kept the bolt from hitting your face? When I had my complete head separation on that .22-250, the case came out of the chamber pretty easily at home by making a little hook out of stiff wire and snagging the case mouth from the rear. I've also heard of jamming an oversize brass brush into the case and then pulling it back out.
I too have no idea what the min or max thread dimensions for your Springfield would be. From some articles I read by Frank DeHaas and others on blow-up testing of the Weatherby Mk V action, there was only slight expansion of the barrel just ahead of the receiver ring when pressures exceeded 100,000psi by firing a standard 78 gr- IMR 4350- 180 gr bullet load in a .300 Weatherby Mag into another 180gr bullet that was jammed into the throat. It increased from 1.147" to 1.1496"... nothing you'd see just by looking. Other sources tell of Remington 700's that had a .308" bullet fired down a .270 bore without blowing up the barrel, and 6.5 m/m Arisaka's that were rechambered to 6.5-06 and later fired with standard .30-06 ammo without changing bore or chamber dimensions. I also saw recommended 4895 loads of 47 grs. for a 150 gr. bullet at around 2700fps, so I'd assume Michael's 44 gr. load was moderate, and not much reduced.
I understand your reluctance to shoot any more low number Springfield's again. It was a number of months before I tried that sporterized VZ-24 after being temporarily blinded by it. The first shots with brand new brass were with the gun tied to a tire and me pulling a long string tied to the trigger... from behind a big oak tree.
