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

[StoneHendge]

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.

I used the 1 ounce Taccom Ultra Lite Weight buffers in my 16" 6 ARC with MLGS an adjustable titanium carrier. They worked great but I bailed on the whole system since the gas screw on the carrier would wander towards less gas. I'm guessing I had the gas open about 30-40% when it was dialed in. I'm sure the buffers would work fine on a .223/5.56. One downside though is that there can be feeding problems if you jam the mag against a barricade or bag and the mag moves in the well and tilts the cartridge nose down slightly. There may not be enough inertia to push it into battery and the round's nose can get caught up on the extension.