I can't answer your question. That said, a more fundamental ones. Simplicity, strength and ergonomics. With emphasis on the latter. As... Why convert? I've had a few '17 Enfield conversions and IF as them, including a "speed striker", by whatever name/term, a quite heavy bolt lift. Yet beyond such 'complications', yet the strategic "Why?" The pasue IF speaking of "bench or prone shooting", simply ignore all of the following. Such positioning where reaching over the bolt from normally passive hand" another case entirely with opposite conclusions. Otherwise, moving right on...
My belief an 'aura' created by the dominance of Springfield '03 and Mauser 98 actions "cock on opening" inherent style. Yet such as P14 & P17 Endfields and their wider Brit gender, not just "sub" said Springfield/Mauser variants not achieving the "cock on opening" pinnacle!
To strip the generations old hype for cock on opening, more fundamentally, what's exactly wrong with "cock on closing". More "aura" than fact! Factually the "cock on opening", as spring tension-loading of striker via torsional force resistance; aka twisting of the rifle and 'of which' the forearm wrist necessarily "resists" that torsion to achieve striker "cocking". Conversely, :cock on closing" presents a linear force moving away from the shoulder to be resisted by holding the rifle quite in the same manner as shooting, resisting the same forces. Striker spring force overcome as 'resisting' rifle moving away from the shoulder. Here, exactly the same resistance as shooting stance accuracy-impairing. Rotational forces introducing a secondary movement direction to be resisted!
But more! The cock on closing requires minimal force for extracting & clearing the spend round from the rifle. Such movement unimpeded by 'other force' duality of overcoming spring resisting cocking. Only in the final moments perhaps 15% or so of bolt achieving battery, does "cocking on closing" striker spring resistance occur. The cock on closing bolt as simpler; not requiring the hardened precision-angled cocking cam notched in the aft bolt body as "cock on opening" mandates.
The 'net' to me, a more natural and less fatiguing "cock on closing" force to overcome. For "senior folks", the considerably less stressful avoidance of rotator cuff forces as itself requiring twisting of vulnerable human skeletal structures in both arms. The bolt to be twisted open and the other arm resisting such torsional movement. The entire large arm (stronger) muscle set employed with "cock on closing" 'linear' system as alternative to 'torsional factors' required of shoulder joint participation.
I personally find it more comfortable and less fatiguing in string-fire rapid follow up shot situations where the rifle preferably not lowered to such as perhaps forty five degrees before ejecting the spent shell. In that forty five degree 'down bubble'
the entire of the bolt mass may also be employed to assist in "cock on closing" effort. The typically 'counter-clockwise "cock on opening" without such benefit as potentially clumsy.
The cock on closing action engineering tending to be a 'bit' potentially stronger, as simpler and more rugged achievable design than the cock on opening. On quality bolt rifles, making perhaps 'no difference' per se. Yet in either the "Mud of Flanders" or in your own shooting field, perhaps the "cock on closing" edge offering that small advantage!
Just my take as begging pardon for any redundancy, etc., as composed & submitted without edit!
Best!
John
