Well my current collection includes well use examples like the DWM Boer M93 Plezier which despite what our BATF says was made and delivered in about 1896 and I recently sold a M93 rifle OVS marked and a Carbine all M93's which of course are the weaker Mauser action all made prior to 1897. The rifles do not have a headspace problem, another is an 1893 Steyr Mdl 1892 made in 1893, OK this one has not had a lot of use but again no problems with headspace.
Like wise the AC11 Martini .303, this one was prooed in 1999 as it had no commercial proofs so had to be proofed before I could buy it from the dealer. It had been found standing in the corner of a basement after the owner in a drunken moment jump off a railway bridge into the path of a train
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I have heard of one dealer who specialises in Enfields who checks headspace and adjusts them to as close to minimum as possible before testing them for accuracy. He shoots all his stock so he can honestly say how them perform on the range.
Using normal ammunition of the correct pressure for the arm causes no problems it's the "expert" who improves upon the loads and has to have it all at Max which normally causes the problems.
Like I say none of my rifles show any signs of headspace problems. Now shotguns are a different kettle of fish entirely due to their design and lock up, side by sides this is of course. here in the UK there are loads of old SxS shotguns made during the very early period of their development but even then I do not hear of many being badley out of spec. Again handloading could be the problem as here in the UK very few people handload fo shotguns, it's just not worth it. These old guns often have the 2 1/2" chambers some may still have the original 2" 12 Bore chambering. Now 2 1/2" chambers is no problem as all shops carry cartridge suitable for them at good prices and I suppose that due to this folks don't seem to feel the need for high pressure high velocity magnum type loads in their old guns. If I want to shoot goose then I break out a baikel O/U which has 2 3/4" chambers and chromed barrels and use a load suitable for the quarry. Due to newish legislation we now have to use non toxic shot for waterfowl even I land and not over water like stubble fields which earlier had been shot over for Pigeon using normal lead shot
My old 1909 Cogswell probably the barrels could not take non toxic shot and I am certainly not going to risk even this cheap gun finding out, so i sue a more modern one instead.
SxS's can quite easily be checked by the owners by hold the action with barrels fitted up to a strong light and looking for the gap, it can also be checked using a ciggerette paper and the gun can be re-tightened on the face by a compentant gunsmith.