I thought I would post a couple of articles about checking cases during reloading.

1. https://sierrabulletsblog.com/2015/08/12/reloading-101-case-diagnostics/

2. http://www.exteriorballistics.com/reloadbasics/caseinspect.cfm

Good info. My thoughts are below and appreciate any "constructive" critique.

1.) Lake City unknown year.
Case #1 was seen to have a very rounded shoulder and split. Upon first look it was obvious that this round had been a victim of excess pressure.

What's strange about this case is that it appears that the crimp is still in place which implies that it hasn't been reloaded, so how might the overpressure occur?

5.) Lake City Match 85
Case #5 appears very much like case #4. The bulge is not as pronounced as on the R-P case, and if fired in the same gun, may simply be because the Lake City case is slightly heavier walled.

Could the apparent bulging be from the FL resizing? My Lee die stops about there (following the Lee instructions) but have never noticed bulging in the area.

Surface Defects
Surface defects include any and all defects on the exterior of the cartridge case. These may range from slight scratches, to severe dents along the case body, shoulder or neck. Small dings and scratches are inevitable (especially when using semi-autos) and of no great consequence.

I commonly have "ejector love taps" on my AR brass. I constantly ponder about the dents and dings that the FL die is not able to iron out. I don't use Varget because it beats the brass to hell, but ARcomp leaves it alone. My understanding is that it's a combination of the powder and the stock spring tension.

Finally, I like watching Johnny's Reloading Bench because he shows his test results rather than make unsubstantiated claims like most videos do. This one has a cautionary tale of an overpressure load. https://youtu.be/h1KJpDyzq0c?list=PLTTrjvDib94mGnOlwzzwOPCreXUiGp1dH

Good info. My thoughts are below and appreciate any "constructive" critique.

What's strange about this case is that it appears that the crimp is still in place which implies that it hasn't been reloaded, so how might the overpressure occur?

An over pressure situation can occur with a cartridge that has a proper amount of powder with the correct weight bullet. The over pressure situation in this particular instance comes from the case deformation due to the case not being properly supported and completely in the chamber when it was lit off. I had a similar situation with a 9mm AR upper I bought a few years ago. The chamber was cut incorrectly and the cartridge was not supported properly. And brand new standard velocity (not +P) cartridge was bulging terribly to almost the point of bursting and the primer was pushed out completely due to the over pressure situation. Over pressure can come from a poorly supported or a out of battery cartridge that is ignited. Not just a cartridge with an incorrect amount (double charge) of powder. This is why you see case bulge and primer flattening to an extreme with a non reloaded round. Basically, when the pressure of the powder ignition is not 100% directed towards the muzzle an over pressure situation occurs.

Could the apparent bulging be from the FL resizing? My Lee die stops about there (following the Lee instructions) but have never noticed bulging in the area.

No. The bulging occurred due to a chamber being on the large side of within the SAAMI specification. The case bulged into the excessively large chamber. Both #4 and #5 are caused by the same reason. The case you see in the photo shows the bulge before FL sizing, not after.

I commonly have "ejector love taps" on my AR brass. I constantly ponder about the dents and dings that the FL die is not able to iron out. I don't use Varget because it beats the brass to hell, but ARcomp leaves it alone. My understanding is that it's a combination of the powder and the stock spring tension.

Every gun/powder/ejector etc. combination will show different damage to spent cases. I take each piece of brass on a case by case basis. For dents I roll the case on a flat surface. If the dent is minor in nature and the case is still straight and not reloaded numerous times I will reload it. If the dent is major and/or the case is not true I will toss the case. Tossing a suspect case is cheap insurance. I have had cases where the dent was so pronounced it caused the case to bend slightly. Even after FL sizing the case was not true. It killed me to toss those (obsolete caliber) cases at $1-$2 a piece. But safety is tantamount to me.

Finally, I like watching Johnny's Reloading Bench because he shows his test results rather than make unsubstantiated claims like most videos do. This one has a cautionary tale of an overpressure load. https://youtu.be/h1KJpDyzq0c?list=PLTTrjvDib94mGnOlwzzwOPCreXUiGp1dH

I'm not familiar with that person but I will check out the link you provided.