If you have ever looked at the end of a R700 barrel you would know this is not true.
Here is the tenon on a 700 barrel and the nose of the bolt that fits into the counter bore of the breech end of the barrel. The headspace gauge duplicates the cartridge. You can see that you would have to go through the threads on the barrel, then you would have to go through the nose of the bolt that goes into the counter bore near the chamber. The bolt nose, the counter bore in the breech of the barrel and the action diameter are the 3 rings that Remington touts as a safety design. The whole you would need to drill would be at least .200"-.250" below the face of the gauge or barrel.
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Furthermore, I don't know what you think you see when looking in the gas relief hole but I can tell you it wasn't the cartridge. That hole is closely aligned with the whole you see on the side of the bolt head in the picture above which is designed to relieve any pressure that enters the inside of the bolt from a catastrophic event or pierced primer.