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Is it normal for a rifle (243 Model 70) to have the stretch mark before the extractor groove not be concentric? IE it is only stretched about half way around the cartridge. The other half looks untouched. Accuracy issues..

Perfectly normal. The cause can vary . First, it is important to understand that some clearance is normal and necessary. The case will expand to fill the chamber and such expansion may or may not be concentric. Reasons for eccentric expansion would be:
Brass which is thinner on one side or
Extractor pushing the case to one side, or
Bolt face not concentric to the chamber or
Things I can't theorize about!
Although possible, it is unlikely this is the source of any inaccuracy. There may be some relationship but inaccuracy is usually the fault of the barrel. the bedding, or the ammunition. GD

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Normal.

Understand that, for the cartridge to enter the chamber freely, the chamber needs to be slightly larger in diameter than the cartridge, so,prior to firing the cartridge actually lies in the bottom of the chamber, with no space @ the bottom and just a little atop.
Ergo, the brass expands upward.


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I can understand the reasons for it not to be concentric, but this rifle is the only of many that I have owned that is not concentric. At least not so noticeable only one sided.