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Why did bolt guns evolve toward cock on opening?]
IMO, Paul Mauser had some reason to switch to cock on opening in 1898 - otherwise all 98's would be cock on closing.
Don't forget, Mauser's M1898 upgrades were all about safety, like 3rd locking lug, gas relief ports, interference lugs on the front end of the FP. the flared bolt sleeve for gas diversion, etc, etc.
One reason for a safety change is that in the Mauser design, the firing pin extends out at full length to fire a round.
In the cock-on-closing design, if the firing pin didn't get cocked, or catch on the sear, as the bolt was closed, the gun might fire before the locking lugs engaged.
"Cock-on-closing" depends upon interaction between two separate entities - the sear (in the receiver lower tang) and the FP ( in the moving/manipulated bolt).
"Cock-on-opening" depends upon interaction between two separate parts of the same entity - the nose of the FP's cocking piece, and the notch in the bolt sleeve/shroud - both attached to te bolt.
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