Many of us run compressed loads and don’t see this. Reloading manuals don’t warn against them and often list them marked as such (C).
I guess with a fast buring powder you might see it?
We work up loads to the point they are compressed and never see any pressure spiking. How/why does the powder need space? There was no sign of spring back on the round showed. You could get some spiking IF you REALLY compressed the round but to do that there would be spring back.
Belmont was not talking about compressed loads. He was talking about the case volume. A load is developed with a certain case volume in mind. If you burn X amount of powder in case volume Y and then you burn the same X amount of powder in a case volume of Y - S (S = loss of space due to bullet setback), you will get a higher pressure in the second case of Y - S case volume. That is what he was talking about. Nothing to do with compressed loads.
Also, there is obvious bullet setback in the picture shown from this incident.
The bullet ogive has started in already at the case mouth.
Working to a compressed load lowers volume. Why do we not see any spiking as has happened in this case?
We are talking a MASSIVE spike here. What’s different?
That looks to be loaded to 80% or higher volume so it’s not a fast powder (which WILL spike fast and hard). No spring back on the projectile so it’s not compressed that much is it?
The P/T graphs I have seen do show some small spiking when set back happens. Nothing of this size though.
No, it does not. A compressed load has nothing to do with lower case volume.
A compressed load results in denser powder.
Case volume is the same for a compressed load or an uncompressed load for a given case / bullet combo seated to the “standard” depth for that sort of bullet.
Why do we not see any spiking as has happened in this case?
For what, your compressed loads? Different problem and nothing to do with bullet setback.
We are talking a MASSIVE spike here. What’s different?
That looks to be loaded to 80% or higher volume so it’s not a fast powder (which WILL spike fast and hard). No spring back on the projectile so it’s not compressed that much is it?
compressed is irrelevant.
And for rifle powders, 223 powders are relatively fast in a relatively small case.
The P/T graphs I have seen do show some small spiking when set back happens. Nothing of this size though.
In the picture below we are not talking a setback of a few 1000s of an inch. We are talking a comparatively serious amount of case volume reduction.
I don’t think propellant had anything to do with it. I think it was just a bad case. This illustrates how effectively the cartridge case seals the chamber and what happens if it fails.
I don’t think so. The evidence says otherwise. The evidence shows huge overpressure.
The splitting of the barrel extension, for example, would not have happened with just a failed case blowing back into the upper.
The other round shown, which appears to come from the same ammo source, shows excessive bullet setback. My understanding is that that can lead to overpressure.
While 44 Mag is not as high a pressure cartridge as 223, it is high. I was shooting 44 Mag (at Magnum pressures – very stout loads) and had a case rupture in the side. Probably a bad case by looking at the split. I did not even notice it until I tried to eject the brass and had one sticking some. The gun was not blown apart and the cylinder is not as thick of metal as the barrel extension.
I know this was mentioned in another thread but here is the Remington notice for this particular ammo
We don’t know if this guy had something from that lot. It says “improperly loaded”. That could be anything from too much powder, to improper crimp or neck tension, to wrong powder.
Ah, you were making a point about the crimp. No need to eat crow, it was a mis-understanding on my part.
If you study the photo, you will see the nose of the bullet is mashed. This cartridge shows signs of having been slammed around in the magazine when the accident happened. It did not leave the factory in that condition. If the bullet was pushed back and that badly smashed by simply being chambered from the magazine, that rifle had serious feed problems.
Again, it’s possible high pressures resulted in the bullet being seated too deeply but it’s highly unlikely! The reason being is that the deep seating would create a freebore condition which lowers pressures.
It’s possible the accident resulted from the problems the ammo is being recalled for plus a tight chamber
This is not the issue here. That projectile is now soft seated and will move out before volume becomes an issue.
I REALLY think this was a load issue. You don’t get spikes that big in this situation. It does not happen. I know how to make it happen though. Many of us also replicate this same enviroment and it’s “safe”. Those that change case volume on max loads find pressure issues. Possibly hard to lift bolt UNLESS they use the wrong powder. Once you do that you are in real trouble.
I’m not “arguing”, it’s just that the only way I know of to get this to happen is powder choice or “other” factors.
I also understand what I was trying to say and what it seemed I was saying did not match. That’s what happens when you post tired 
I spent a little time playing with Quickload tonight looking at how seating depth impacts chamber pressure. According to Quickload loading SAAMI spec 223 with 22.5gr of Hodgdon H335 and a 62gr Remington HP match bullet the chamber pressure is:
39162 psi seated .25" (amount of bullet seated into case)
40557 psi seated .30"
42081 psi seated .35"
43738 psi seated .40"
All of the above assume that you are shooting in a .223 Remington chamber, pressure will be lower in a 5.56 chamber. I could be wrong but I don’t think the increase in pressure is enough to split the carrier and upper like the photos show.
I know we don’t have all the info here. But, I wonder if he had a squib round in the barrel? Especially with that amount of damage to the barrel and BCG.
Sort of like this guy???
Just to throw this out there, but I had a failure to eject that resulted in the follow up round being as compressed as the picture in question. That was with a standard carbine buffer, and I’m thinking that this suggests that it may not be a feed problem. Why? Because I have seen a carbine buffer compress a round that much. I imagine that if the bullet wasn’t seated properly, that just hitting the feed ramps (or in the case of a cheaper rifle, lack there of) could be enough to cause this compression.
But I am far far from an expert, and am just hypothesizing.
In regards to the thread as a whole this has been very informative and I have learned a lot. Thanks guys!