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um, just for clarification, I don't know much about powders, I found links to an "Accurate 5744" powder but not a 5477. Am I just not finding the right stuff?

Yes, my mistake. That is the powder.

Thanks for posting, glad you are ok.

I wonder if your blow up up was caused by the much debated but never proved case of too much air space in the case.
Regards.

Nero, you might have something there, but I'll let others figure it out. I won't fire another low number 03 again. I made a carefully considered decision when I decided to shoot mine, but I would not make the same decision after this experience.

Everyone has to make their own decisions about this and I won't criticize anyone that feels that he should do as I did and shoot a low numbered rifle, but I just won't do it again. I posted this note because I want everyone to have the best information moving forward, regardless of what you decide to do.

I do wish Michael was around to talk about this. I don't blame him in the slightest, but I wonder what he would have said about it.

Additional thoughts:
Just as I posted this originally, it occurred to me that if this was a case of powder detonation as claimed by some where there is large air spaced in the cartridge case, then the barrel probably should have blown, yet the receiver is what went to pieces and the barrel is almost good enough to reuse. Had this been a powder detonation, I think the barrel and chamber area would be badly ruptured. So, in re-reconsideration, I believe this is NOT an instance of detonation.

Lots of clues here, but not nearly enough information to really make any judgement. Having the receiver grenade to pieces suggests improper heat treatment, but there are merely vague clues as to what caused it to fragment. A complete head separation is more likely to be a sign of excessive headspace than high pressure. That can be a defect in the gun, or from using brass that is somewhat brittle and has had the shoulder set back too much during resizing. I had the latter happen with a VZ-24 Mauser rebarreled to .22-250 when I foolishly used some old brass a buddy gave me. Primers of the two cases fired prior to the head separation were flattened severely even though the load wasn't hot. But it was a lot warmer than this 5744 cast bullet load rated at 30,00 psi. Yet there was no damage to my gun. Plenty of gas escaped, and I was totally blinded for about 20-30 minutes and had numerous brass and powder particles hit my face. After I began seeing slight blips of light, it took about another 30 minutes for my vision to clear up. Young and dumb, I had no shooting glasses on at the time. Later firing with brand new brass that was properly resized for my chamber was no problem at all.

During a head separation like that, the case head is unsupported by the bolt face because the firing pin pushes it forward in the chamber perhaps several thousandths of an inch until the shoulder stops it. When the primer detonates and ignites the powder, the case expands and seizes the walls of the chamber. The unsupported head slams back into the bolt face, and this is what flattens the primer. Normally, with fresh brass, the case stretches and there is no problem at the time, but it might partly or completely separate after more reloading when the shoulder is again set too far back during resizing.

So was that sudden impact from the case head slamming the bolt face enough thrust to shatter the action on this low number Springfield? Or did the threaded portion of the barrel expand slightly due to excessive pressure... even though it appears un-deformed and not bulged. You would need before and after measurements to know for certain. If there was some slight expansion, then I would suspect either some detonation phenomena due to excessive air space... or an accidental double charge.

I'm wondering what kind of pressures the 44 gr. of 4895 charge under a 150 gr bullet that Michael used in this same rifle developed? Certainly more than the 30,000 psi from the Accurate 5744 load, That is pretty mild to do the type of damage described. This is why I hate even using any loads that will not overfill the case with an accidental double charge. But of course, I have done it thousands of times, especially with handgun reloads. Any of us can get distracted and make a mistake. That leads to the question of what pressure a double charge of this 5744 would develop. Would it actually be enough to rupture the chamber, or more likely, just enough to slightly expand it and shatter a somewhat brittle receiver? I would want to carefully measure the barrel thread diameter, and pour a Cerrosafe cast to verify that chamber dimensions have not expanded slightly. Maybe insert one of the previous fired cases all the way and check for any slight wiggle or slop. Even with a double charge, I would not expect any dimensional difference in the chamber area that you could see without measuring. But the grenade-like damage described here doesn't inspire me to want to shoot low number Springfields. I'm thinking of P.O. Ackley's action strength tests where he progressively loaded hotter and hotter loads in numerous rifles all chambered in .30-06. The action from a 6.5 m/m Type 38 Jap Arisaka was the last man standing, and finally, he filled a case with some pistol powder and weakened the case head by filing a notch in it. When he fired it with a long string on the trigger, the barrel threads stripped and sent the barrel down range. But the Arisaka action held.

I tend to agree with Nero. Read about S.E.E
Secondary Explosion Effect.
But yet, I seem to recall Bill Roberts telling me years ago that some early '03 Springfield had case harden issues - being too hard and came apart; maybe similar to this?
Hate to hear any such story - Glad you are ok to shoot another day.

I first heard of S.E.E. years ago when using WW 296 in my .357 magnum. I've read a lot about it and I just read several more articles on S.E.E.

One recurring theme was that ballistics labs have not been able to duplicate it with the same loads that allegedly blew up guns. Didn't matter if it was reduced loads of slow or fast burning powder... magnum primers or standard... powder tipped forward in the case or to the rear. The one common theme was that in virtually all instances, there was enough room in the cartridge case to fit an inadvertent double charge.

I'm not going to be one of those guys who absolutely scoffs at the notion of S.E.E. I believe that it does indeed happen with reduced loads of some powders like WW 296 or H 110. I also know there is weird stuff that happens with degraded powders and powders that are jostled and reduced to dust and have their deterrent coatings worn off. But 28 grs. of 5744 in a .30-06 case isn't a severe reduction like some more risky loads of fast powders that utilize 10% case volume. And when real detonation of powder does apparently happen, the results are catastrophic with chambers that rupture and peel like a banana, and case heads that become fused to the bolt face, i.e., enormously high pressures. This particular low number Springfield is said to have a barrel that, visually at least, looks like it could be reused. But we have heard about the improper heat treatment of some low number Springfields forever. I recall reading about one that shattered when a center punch was used to mark the receiver ring for drilling scope mount holes.

I think I can rule out the headspace problem as I understand it.

First, the brass was Winchester brass that had been previously fire one time only, and the same rifle. Thus, it was well fire formed to the chamber. It had been annealed before the first and and second loads in my annealing machine. I have great faith that it was neither over or under annealed.

More importantly, I was using a lead bullet (approximately Lyman #2 alloy for hardness), which I had loaded a bit longer than MOA so that they were forced into the rifling. This made the bolt hard to close because the lead was lightly engraved on the first band and nose and the bullets, being tumble lubed, had to negotiate that sticky nose into the rifling. There is no chance that the brass was anywhere but against the bolt face when the primer stuck.

Because the bullet was well engaged in the throat, there is also very little chance, in my mind, that the firing pin could have moved the case forward before detonating the primer. If this was happening, the primer strikes on the prior rounds would be quite light, but they are not.

Perhaps engaging the rifling with the bullet increased the pressures substantially. I have my doubts about this since breech seating procedures that do the same thing to a greater degree are widely practiced in the Schuetzen world where I sometimes hang out.

So, in sum, I think we can rule out headspace as the cause.

I will measure across the threads of the barrel and see what I find.

The remains of the blown round are still in the chamber so trying to fit a piece of brass in there is not possible. I have not tried to extract the brass. BTW, all the previously fired rounds had extracted normally with ease.

I am on the fence about these SEE events. Maybe, maybe not, but several folks have independently informed me about 5744 being a bit "tricky" in that it seems to have produced other unusual and rare events that might be signs of high pressure issues in seemingly normal loads.

The barrel's threads measure about 1.04" across the tops of the threads, though that measurement is tough to precisely for some reason. Behind the threads, over the funneled part of the barrel, it measures 0.999". In front of the shoulder it measures 1.145".

There is a little damage to the funneled part of the barrel. It looks like it took some impact with the concrete, and maybe some other metal pieces which made nicks and dents, but clearly, the barrel does not appear to be expanded in any significant way.

I don't know what "normal" should be for these measurements, but that's what I have on this one.

I sure would like to know the pressures that Michael's load developed. Does anyone have a book with pressure numbers for that load?