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And if so, why was it made so? And what about the 7.62mm NATO, then? That's 11.9 & 12, rounded, up/down!? And why doesn't it have SR in the title, then!? It's not! Just look at the Image/s, of it. Unlike the Japanese 6.5x50 mm SR, whose rim is just 0.5 mm wider, and U can actually see it. Actually, the actual/correct measurements are 11.25 & 11.38, so it is a bit rimmed: 0.13 / 2 = 0.065 mm. It's just the high taper of the case. There was a rimmed version, in the beginning, and a commercial semi-rimmed later, on?

 — Preceding unsigned comment added by 220.101.38.242 (talk) 04:56, 7 September 2019 (UTC)[reply] 

I wasn’t sure if this would work better as a reply to the previous topic or as a standalone. The cartridge is a true rimless cartridge as we understand it today. If you continue the line of the taper, it comes out at the rim diameter. If you touch original cartridges together, the case walls make full contact. If you touch modern RCC cases based on the French drawing seen in this article, the case walls make full contact. I suspect the confusion either comes from the semi-rim added to .220 Swift or the terminology of the time. “Semi-rimmed” was sometimes used early on in the smokeless era to refer to cartridges that we’d now call rimless. The original Winchester drawings for the cartridge refer to it as “headless”. Tenacious Trilobite (talk) 14:06, 20 June 2025 (UTC)[reply]