I wonder what chamber they were using with that rifle. Doesn't say in the thread. The 123gr AMAX has a more sharp nose profile and is more forgiving of short throats, whereas the PPU 120gr MPT is a tangent ogive that will jam the lands much sooner.
It looks like the case failed at the web, and is belted. That points to early and violent extraction, which is usually a symptom of very high port pressure.
Another problem with using a large rifle primer is that there is less mass in the brass case to act as a heat sink. Even still, this should not be happening with factory ammo, heat or no heat.
I just noticed something in that thread. The OP doesn't specifically state which PPU ammunition was being used, and I saw something in the background of this photo that caught my attention:
Anybody notice the type of projectile on that cartridge in the background...
Looks like the 123gr PPU Soft Point, which we haven't seen in a long time. That load was a notorious bad performer for most on the board dating back to the first Grendel Forum. It wouldn't chamber in a lot of guns, and those that did, it was jammed into the lands often.
It looks like the case failed at the web, and is belted. That points to early and violent extraction, which is usually a symptom of very high port pressure.
Another problem with using a large rifle primer is that there is less mass in the brass case to act as a heat sink. Even still, this should not be happening with factory ammo, heat or no heat.
I just noticed something in that thread. The OP doesn't specifically state which PPU ammunition was being used, and I saw something in the background of this photo that caught my attention:
Anybody notice the type of projectile on that cartridge in the background...
Looks like the 123gr PPU Soft Point, which we haven't seen in a long time. That load was a notorious bad performer for most on the board dating back to the first Grendel Forum. It wouldn't chamber in a lot of guns, and those that did, it was jammed into the lands often.
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