I had a partial case head separation using a 1.8oz buffer

[LRRPF52]

The feed cones on that Odin throat look to be quite a bit deeper than the other 2.

Since I don’t have anything in my hands, I won’t say anything definitive about the geometry of that chamber, but it does appear that way at least in the photos.

The feed cone appears to be more generous and at a different, shallower angle.

Could be the lighting, but that’s how it appears in those images.

Also, it’s possible that the tiny buffer and spring would work with 5.56 or .223 Rem shooting 55gr, but I don’t think I’ve ever seen buffers that light.

The only one I can think of off the top of my head was the nylon buffer KAC experimented with on the SR-25K back in the early-mid 1990s right as the Clinton AWB was looming.

It didn’t work out.

ArmaLite Inc. (Really Eagle Arms with lots of work done by Karl Lewis) developed a longer RET for their AR-10 carbines, now referred to as an A5 RET that has become popular in AR-15s with a longer-than-carbine length buffer, but shorter than rifle. That helped get reliability where it needed to be on 7.62 NATO carbines, which was very elusive originally.

The Dutch built some rare AR-10 carbines, but kept full-length stocks on them. Those buffers and RETs are larger diameter than AR-15 or SR-25.