If memory serves me, the Zastava actions were the basis of the old "Whitworth" .458's, .375's, etc.
FYI--
Just read an article by Boddington who tested the new Mauser 798 Remington--and yes it is a Mark X action as you suggested...this article took place in Namibia--they had a gun crew over there shooting plains game.. in the article he did mention that Lott built several guns on this same action for himself..
Personally, I am still reserving judgement until I see one in person--
Ripp
-------------------- ALL MEN DIE, BUT FEW MEN TRULY LIVE..