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In any case, there's eight "spokes." A double C broad arrow would have six. Plus the apex of the arrow isn't at the centre of the "C" on the stamp, it's at the top 1/4.
The angles look wrong too for a C broad arrow stamp... too wide on the "arrows"... but if a stamp with funky angles was stamped 4 times around in a circle you could get this pattern, and a circle in the middle where the tips intersected. If it's struck four times though, someone did a really great job of it as I don't see any overlap.
I have been actively collecting Lee Metfords and Enfields for over thirty years. I never turn down an opportunity to check out the markings on a Lee, even poor Bubba specials if offered. I have not seen this mark in the metal of a rifle before now.
You mention that it is on an EAL rifle? If so, the mark might not be military.
It would appear to be similar to commercial made stamps retailed to hobbiests for leather working. No doubt similar are available for metal workers and jewellery crafters.